Elrenu
Official Completionist Seal of Approval
These mashups are ridiculous, that's the point, some may be cheesy in quality and in that case it's probably because I rushed, or because I don't care. 
Kana Hanazawa, Was (Not Was), Bubba Sparxx, Wii Sports, Reese's Puffs, Sonic Adventure, Cory In The House, Mucha Lucha!, Ludacris, Foster's Home For Imaginary Friends, Psy, Mark Ronson & Bruno Mars
(This one I find a bit messy, but people seem to like it.)
Lucky Star, Sonic Adventure 2
(Already in the forums, don't remember the rules about posting the same video more than once, so I decided not to embed this one. Anyone can correct me and I will embed it.)
Baka and Test, Haruhi Suzumiya
K.K. Slider, Will Smith
Sonic Adventure 2, Final Fantasy IX
Sonic Generations, Ludacris
(Messy, but I feel the song in itself is, still, something I could improve with more focus.)
My Life as a Teenage Robot, Daft Punk
(Absolutely messy, but I don't plan on ever touching it again.)
(This one I find a bit messy, but people seem to like it.)
Lucky Star, Sonic Adventure 2
(Already in the forums, don't remember the rules about posting the same video more than once, so I decided not to embed this one. Anyone can correct me and I will embed it.)
(Messy, but I feel the song in itself is, still, something I could improve with more focus.)
(Absolutely messy, but I don't plan on ever touching it again.)