Awesomenauts is a lot of fun, and pretty fast-paced for a MOBA. I love the cartoon style they go for, which already makes it a several times more interesting than your typical cool/dark MOBA. And the music themes, oh man.
http://www.youtube.com/watch?v=EAifpQmrnSUThis is the theme of Leon Chameleon, a lizard alien assassin with a French accent. If this song doesn't convince you that the game is zany, I don't know what will.
That being said, I suck at this game, so when I settle at rank 5 or 4, I really start to get pummeled by other players.