Don't Stop Believing because I hate Journey. I have most of the songs on my itunes, but there are a few I didn't download because I know I'd never listen to them. Like DSB, Thong Song, Smile (Lily version) and a few others.
Well I've never completely HATED a song that they sing on Glee because I absolutely am in love with that show! But the one song I thought wasn't that great was the beginning of that one episode when Quinn was singing "Don't Stop Believing" with Finn instead of Rachel; she sounded horrible!