Words with Friends is great if you.like scrabble style games and have any Facebook chums who also play, although that's not essential, you can play a random player. It's a bit like a game of postal scrabble because you just get a notification when its your go, you don't have to sit there for hours taking a turn.
Galaxy Tarot is a great little app if you are in to that sort of thing. I have found it remarkably accurate since I have been using it.
Pho.to Lab is good fun, you need to be near a WiFi connection but basically its a piece of software that uses facial recognition software and you upload a photo and it puts the face or sometimes the whole photo or even a range of photos into a scene, hard to explain until you see it, I have had endless fun putting my sons face onto various pictures and there are loads of different ones to choose from.
Will have a think and add any more I can recommend.