I want FUN, free (mostly), games for iPod touch please? suggestions?

So i'm going on a lot of trips this summer and recently got a new ipod touch. I really want some fun, and free games that i can play on the road this summer. Free would be ideal but i can go with 99 cents ones too. Any addiction ones? Oh are they're any that you can't live without? I already have angry birds, facebook, snowboarding, fruit ninja. Thanks!