well i like one of three games....
Zynga poker... very fun for anyone looking to play for fake money
Keno.... Great game, and they have done so much with it.
And WMS gaming slots... One of the most popular slot machine companies from any casino, has a facebook game featuring games like Zeus, King of Africa, Reel em in, Black Knight, Life of Luxury, and Game Of Dragons. The actual name of the facebook game is called "Lucky Cruise" and they constantly update, and add new slots.