Funky stuff is always fun to play, even if you don't particularly like it - go to your tab website and look up some Jamiroquai songs, they have a good mixture of choppy chord progressions and unison riffing. Also check out Prince, I recommend "Computer Blue" and, of course, "Purple Rain".

A metal riff that I find a lot of fun is "Train of Consequences" by Megadeth. It has a great groove to it, and is interesting in that it's mostly played with upstrokes and heavy palm-muting.

Also, I know their songs are piss-easy, but I find Cake songs great fun to play, especially when you're singing/rapping along :D.