The other day my 8 year old wanted to watch a Michael Jackson video on youtube. Weird Al showed up on the sidebar, she asked who it was so we watched it. It was kinda cool because I was about her age when he started making all those goofy knockoffs. Tenacious D is funny too. But I'm voting for Weird Al for nostalgia.
Absolutely no contest. Weird Al in a landslide. Tenacious D are not funny, and Jack Black's schtick (other than High Fidelity) is grating and painful to watch. Now if you had made this a Flight of the Conchords vs. Weird Al, I would have had a much more difficult time deciding who to vote for.