I'm going to be stereotypical and say......
Battles 
god, I'm predictable. I would have voted for Kayo Dot or TMV but you can only pick one, and Battles got me into post-rock, so I owe quite a bit to them.
And I'm never going to vote Muse because they have these boring, generic tendencies, and the song they did for twilight made me frown the entire time it was on the radio at school. I don't know why, but Muse just has no appeal to me whatsoever, and I'm a big prog fan