I like trivia games, so I play Sporcle. Risk, Uno, Fragger, Pocket God, Annoying Orange Kitchen Carnage, Fruit Ninja, Bloons TD 4, Stair Dismount, and Life are all fun.
Ha, I love Fruit Ninja <3 (I'm such a simple person. ) I think Traffic Rush is okay, it makes you strategize! Oh, and Doodle Jump! That's a must_have for any iPod owner.