Woolah - Knockout Photo challenges with your friends.
QuizUp - QuizUp gives you the opportunity to test your trivia skills against friends and strangers throughout the world.
SPAR! - Challenge your friends. Put money on the line. Get better.
A Google a Day - Online trivia game where you use Google's search to answer questions as fast as you can.
Trivia Crack Kingdoms - The amazing quiz game that lets you test your knowledge and challenge your friends to see who is the smartest. Developed by Etermax
ShutterSpots - Find & share photo locations nearby & all over the world!