Weird Al Yankovic? The Lonely Island? Flight of the Conchords? Jonathan Coulton? Tenacious D? Psychostick? Stephen Lynch? Rucka Rucka Ali?
I've been a fan of Weird Al for years now. His older stuff actually holds up surprisingly well, and his last album, "Alpocalypse", was pretty damn solid.
And I absolutely LOVE Tenacious D. I saw them live earlier this year and they totally slew me.