I Love trivia. So I just found this iOS app called Guessomania and its kind of a Trivia App but the experience is much more intended to be social. Furthermore the App is designed as a competitive social game.
The app simply asks some trivial questions and you have to guess its answer the more you play the more you learn something new. Guess what you earn coins for every questions you answer and those coin lets you unlock more questions. You can also share trivia that you like on Facebook.
There are both more paid and free version of this App. The paid version is add-free and has bit extra knowledge packed in. After spending hours on the app its kind of a fun experience plus you earn some knowledge.