There are three main categories of large applications on Facebook: social games, quizzes, and apps that analyze Facebook data to tell you interesting factoids about you and your friends. And on this week’s list of the top 20 fastest-growing applications from AppData, we have all three, although quiz apps have a weaker showing today than they have in recent weeks — perhaps because so many games grew especially fast versus last week?

	Name	MAU	Gain	Gain, %
1.	FishVille	15,958,135	+6,719,437	+42.11
2.	FarmVille	66,841,884	+2,235,168	+3.34
3.	Happy Pets	2,944,542	+2,074,404	+70.45
4.	Moment Of Truth	1,898,873	+1,527,845	+80.46
5.	friend.ly	5,528,493	+1,130,401	+20.45
6.	Café World	29,456,515	+1,015,513	+3.45
7.	Snowball Fight	1,282,695	+947,440	+73.86
8.	Zoo World	2,159,596	+856,129	+39.64
9.	Acımasız Gerçekler	1,282,717	+792,339	+61.77
10.	Champions Online	723,800	+723,726	+99.99
11.	QuizBone	3,727,785	+666,943	+17.89
12.	Happy Aquarium	27,711,859	+657,309	+2.37
13.	Fish Isle	670,536	+648,838	+96.76
14.	Island Paradise	6,709,636	+624,067	+9.30
15.	Diva Life	2,169,692	+579,915	+26.73
16.	Friend Quiz	6,612,565	+525,596	+7.95
17.	Daily Sex Chance	562,954	+525,164	+93.29
18.	Addict	520,295	+520,294	+100.00
19.	Fish Life	2,086,784	+474,936	+22.76
20.	Facebook for iPhone	18,125,967	+438,739	+2.42

At the top of the list is Zynga’s latest game, virtual aquarium simulation FishVille, which swollen by 6.72 million users over the past week to reach 16.0 million monthly actives. Behind it is the company’s FarmVille virtual farming game, which has consistently been adding new users even though it is already by far the largest third-party app on Facebook. It gained 2.24 million to reach 66.8 million monthly actives.

And then we have Happy Pets, the new game from CrowdStar. It grew by an impressive 2.07 million last week to reach 2.94 million. The first game to launch after CrowdStar’s big hit, Happy Aquarium, both the game and the developer look like new and serious contenders.

Then, we have Moment Of Truth, which asks you to provide yes or no answers about randomly-selected friends with questions like “Do you think Jean is hot?” This app was actually made with a white-label app creator called Application Builder (Create Your Own App), which explains why there’s a Turkish version also on today’s list, called Acımasız Gerçekler (“brutal facts,” according to Google Translate).

Others in the friend-data category include friend.ly and Friend Quiz — obviously, the quiz concept ties in nicely with any sort of service that tries to analyze Facebook relationships. So, also notable is QuizBone, another simple quiz-maker.

LOLapps continues to push out graphically-pleasing role-playing games, with a new one called Champions Online growing by all of its 723,000 users this past week, and Diva Life continuing to surge, too.