1. Slots – 52.02%
 
You may have not played Slots on Facebook before but around 70,000 people have played and a whopping  52.02 percent of those users return every single day.  There are two  other games in the leaderboard which are part of this application’s  “network”.  You can play “Scratch and Win” (3rd most engaging  application) and “Pull Tabs” (10th most engaging application), and use  the tokens that you’ve won from those applications to bet on slots.
While it may not be the most popular application on Facebook, the  developers behind this game are most definitely generating some decent  cash flow through repeat users.  Also, given that incentive based  advertising is the most profitable thing on Facebook, owning a leading  gambling application is not a bad position to be in. 
 2. Facebook for BlackBerry Smartphones – 48.9%
 
It’s  not surprising to find a Facebook owned application in this leaderboard  considering that 50 percent of active Facebook users return to the site  daily.  If you have a BlackBerry, there’s a good chance that you’ve  already installed this application.  Out of the 3.5 million users that  have installed the application, 1.7 million are using it daily.  
While it’s not surprising to see a Facebook owned application rank so  highly, it is somewhat surprising that Blackberry users are the most  active mobile Facebook users so far.  If you have a Blackberry and read  this blog, you probably have already installed the Facebook for Blackberry application.  If you haven’t, I seriously suggest you check it out.
 3. Scratch and Win – 47.62%
 
Proving that gambling is a popular activity on Facebook, Scratch and Win  comes in 3rd with 64,888 out of 136,000 monthly active users returning  daily.  Scratch applications have been around the Facebook platform  since early on.  Backstage,  the company behind this application, is sitting on a pretty nice suite  of gambling applications.  When ranking applications for profitability, I  would rank this company up near the top.  
Despite having less than half a million monthly active users, a very  large portion of their users are returning daily, and that is one of the  most important factors when monitizing applications.  If you are in to  lottery tickets, go check out the Scratch and Win application. 
 4. Digsby – 47.3%
 
Digsby  is an extremely popular desktop instant messaging client and was one of  the first, if not the first application to integrate Facebook chat.   Unlike Meebo, who had their instant messaging support shut down, Digsby  has remained functional since their launch.  There is one problem with  the application that I experienced which was that you would be kicked  off of the web version of Facebook as soon as you logged into Digsby.
Regardless, out of the approximately 80,000 users that have taken  advantage of the Facebook/Digsby integration, over 32,000 are logging in  daily, oftentimes more.
 5. Wordscraper – 42.1%
 
When  the Agarwalla brothers had Scrabulous shut down, it was one of the most  buzzed about news stories among technology news sources.  Today, the  brothers still hold some of the most engaging applications on the  Facebook platform including Wordscraper  which ranks above both official Scrabble applications.  It was a swift  shift from Scrabulous to Wordscraper, and the brothers made enough  changes to avoid a future law suit.
Now the brothers have the top ranking word games on the platform and  they aren’t complaining.  While the law suits brought much unnecessary  attention to the brothers, the buzz helped attract attention to their  new games.  While they may have been temporarily knocked down, the  brothers are truly masters at developing word games.
 6. Facebook Toolbar for Firefox – 40.53%
 
It’s  not surprising to see Facebook applications rank among the most  engaging applications on Facebook.  Perhaps it’s not even fair to  include this in the list as desktop applications tend to receive a  higher level of engagement.  If you haven’t tried out the Facebook toolbar for Firefox,  I suggest trying it out.  It lets you know about new pokes, friend  requests, messages, event invitations, and group invitations.
Then again if you have a ton of unopened messages and requests like I  do, it may become a bit annoying to have the toolbar.  If you are  obsessive about cleaning out your requests though, this toolbar will  come in handy.  
 7. Super Scratch Offs – 39.9%
 
Yes,  another scratch off application.  It appears that Facebook users are  really in to gambling, or at least competing for reward points.  This is  the second most engaging scratch off game on Facebook and currently it  has just under 140,000 monthly active users.  Around 55,000 users return  daily to see if they’ve won their daily scratch ticket.  Clearly the  developers of the scratch off games are laughing all the way to the bank  as these users don’t seem to go away.
So you may be wondering what you can win by playing Super Scratch Offs.   Virtual gifts!  Yes, you heard that right.  Users are returning every  day to play Super Scratch Offs for the chance to purchase virtual gifts.   It’s almost like a Chucky Cheese’s model or Dave and Busters, except  in this game you can’t win any real candy. 
 8. Dungeons & Dragons: Tiny Adventures – 39.86%
 
I  bet you didn’t realize that there were some uber geeks on Facebook.   Hasbro got creative on Facebook and their subsidiary Wizards of the  Coast, launched the a Facebook version of Dungeons and Dragons.   The game reminds me of the old choose your own adventure books in  which your character had hit points and various other variables which  determined the outcome of battles along the way.  
These adventures have around 6 steps which is why the application is  called “Tiny Adventures”.  It’s a traditional fantasy game similar in  some ways to Mob Wars and other strategy games on Facebook.  This  application is ultimately a big advertisement for Dungeons & Dragons  but almost 30,000 users keep coming back every day. 
 9. Egg Breaker – 39.85%
 
Egg Breaker  is a game which continues to rise in popularity.  Essentially it’s a  new twist on the scratch off games.  You click on eggs to break them and  you can win gold, pieces of a star, virtual gifts, and points.  Each  day you are given a limited number of hammers to go and crack eggs in  the game.  Some eggs are harder to crack then others.  You can also  progress to new levels but I wasn’t completely clear about what  triggered access to new levels.
Once you run out of hammers you can either wait a day or proceed to  purchase more hammers with real money, gold that you’ve won in the game,  by installing applications, or completing offers.  So what can you buy  with all of the gold that you won aside from new hammers?  Virtual gifts  of course! 
 10. Pull Tabs – 39.6%
 
By now you should be able to guess what type of game Pull Tabs  is.  It’s another lottery game but instead of scratching a ticket, you  can pull off tabs on a ticket!  Just like the other lottery games, you  get to spend your winnings on virtual gifts.  You can also send pull tab  cards as gifts to other friends.  One of the biggest incentives for  playing the game is to get more credits to purchase pull tab tickets  with higher payouts.
Many of the pull tab tickets are branded, including one which is  branded for the movie iRobot.  The application is well developed and  it’s not surprising that this is one of the more popular “gambling”  applications on Facebook.
 11. Facebook for Palm – 39.1%
 
I don’t really need to elaborate on this one.  First of all I should add that Palm sucks 

    If you are one of the few Palm enthusiasts though and you read this  blog, there’s a good chance that you are one of the 115,000 people that  have used this application in the past month.  It appears that no matter  what mobile device you prefer, Facebook tends to be one of the most  popular applications.  That’s not surprising considering that there are  over 4 million daily Facebook mobile user.  
As we highlighted last night, mobile is probably the fastest growing  area (percentage wise) for Facebook despite the addition of over 450,000  new Facebook users each day.  Anyways, if you are a Palm user, go check  out the Facebook for Palm application.
 12. Super Slot Machines – 38.8%
 
Are  you serious, another gambling application?  Yes, and we aren’t done  with them yet.  If you are the type of person to scratch off tickets  then maybe you’ll enjoy playing slots.  Just like all the other gambling  games, the premise is the same.  You play for tokens that you can in  turn exchange for virtual gifts.  Thankfully you don’t actually lose  your tokens though.
You spend your credits for a chance to win more prize tokens.  When I  played the game I was one of the day’s big winners and I felt extremely  proud about that fact.  I walked away with a whopping 303 prize tokens  after my first attempt.  So if pull tickets are your type of game, go  check out the Super Slot Machines application. 
 13. Slot Machine Bandit – 38.7%
 
I  swear this is the last gambling application!  There’s really not much  to say about this one.  It’s pretty much the same thing as Super Slot  Machines except the design isn’t as nice.  There also doesn’t appear to  be any fun sound effects which was a little disappointing.  Also  disappointing was that I didn’t win as much money as I did in Super Slot  Machines.  
If the developers of this application boost the odds a bit, I would  guess more users would come back to play on a regular basis.  Then  again, the streaming notifications about other users winning the jackpot  keeps you pulling on the slot machine handle.  I won’t be coming back  to this application but that’s not stopping over 26,000 people from  returning to Slot Machin Bandit daily.
 14. Parking Wars – 36.7%
 
A&E Network must be happy that they decided to launch the Parking Wars application  to promote the Parking Wars television show.  While I don’t remember  the television show, I definitely remember when this game was released  over one year ago!  More then one year later, the application attracts  close to 110,000 people daily.
It’s an impressive feat which is hard to duplicate.  It’s rare that  branded Facebook applications succeed as much as this one.  Thanks to  the right timing and a good development team, Parking Wars remains to be  one of the most engaging Facebook applications.  
 15. SCRABBLE Beta – 34.6%
 
While  the Agarwalla brothers still have the most engaging word game on  Facebook, Electronic Arts has done a good job with their Hasbro licensed  version of SCRABBLE.  The application has almost 200,000 users  returning to the application daily.  It’s an impressive feat for any  developer even if it’s one of the largest gaming companies in the world  that developed it.  
The application has been in “Beta” for months now so I’m not sure if  the company ever plans on changing that.  Scrabble is clearly a popular  game and Facebook has proved to be a great platform for creating  turn-based games like Scrabble.  If “Wordscraper” wasn’t good enough for  you, you can check out Scrabble Beta if you are in the U.S. or Canada.
 16. Pet Society – 34.34%
 
Playfish  is currently the second largest application developer on Facebook based  on daily active users and their game Pet Society is the largest  application based on daily active users.  As I previously wrote, social  games tend to be the most engaging applications on Facebook and Playfish  is dominating this space with Zynga.  
Pet Society is essentially a much more robust version of (fluff)  Friends which let you create a pet and care for it.  The application  includes games for you to play with your pet inside of a large virtual  world.  As you travel around you can win gold that can be used to buy  items to decorate your house. There is honestly more stuff to do in the  game then I had time to check out but it’s not surprising that this game  is the most visited game on Facebook. 
 The game continues to grow by leaps and bounds, currently attracting  over 2.3 million daily active users.  If you haven’t played Pet Society yet, I recommend checking it out.
 17. MouseHunt – 34.32%
 Mouse Hunt has been a huge success.  Since the launch, the application has  continue to surge in popularity.  The developers of MouseHunt were also  winners of the FB Fund.  MouseHunt is a highly addictive strategy game  in which you try to catch as many mice as possible, all of which have  highly detailed designs.  The game currently attracts over 107,000 daily  active users and continues to grow week after week.
 With cash in the bank and a continuously growing application, my  guess is that the developers of MouseHunt have a bright future ahead of  them.
 18. SCRABBLE® Worldwide – 34.30%
 
There  isn’t much I need to say about this one.  Scrabble Worldwide is a  duplicate of the SCRABBLE Beta application except it’s licensed for  users outside of the U.S. and Canada.  Determining which version of  Scrabble you’d like to play is pretty much based on your location and  whether or not you want to play the “official” version or the version  licensed by the Agarwalla brothers.
If you are outside the U.S. and Canada and prefer playing officially licensed games, check out Scrabble Worldwide.
 19. My Fairyland – 33.5%
 
Taking inspiration from the Grow-a-Gift application, My Fairyland is an application that lets you create your own garden to grow flowers  and fairies.  You can also help out your friends by watering their  gardens as well.  This application is nowhere near as robust as some of  the applications we’ve looked at but around 68,000 people continue to  return to this application daily ranking it in our list of the most  engaging Facebook applications.
If you are into flowers and fairies, then I suggest checking out this application!
 20. Facebook for iPhone – 33.2%
 
Last on our top 20 most engaging Facebook applications is Facebook for iPhone.   This one has clearly been a hit.  It’s also somewhat surprising to see  that the Blackberry users use their mobile Facebook application more  often then iPhone users.  Despite the surprise, the Facebook for iPhone  application is one of the most popular iPhone applications ever with  over 5.2 million users and it continues to grow daily.  
If you have an iPhone then there’s a good chance you’ve already  downloaded this application.  If not, you should definitely download it!
Acknowledgement to: