Here are some of mine:
Mega Move (The Adventures of Super Mario Bros. 3) - YouTube
Although frankly I prefer the instrumental version that's used in a ton of DiC cartoons when they're removing the licensed music from DVD releases. I should thank The Annotated Series for bringing this one to my attention :3 Actually a fair few of the songs from the DiC cartoons (mainly Super Mario Bros 3 and Super Mario World) would qualify.
Fab Morvan (ex-MILLI VANILLI) "Girl You Know It's True" (LIVE 2008) - YouTube
Yep, one of the former "members" of Milli Vanilli actually singing one of their songs, and actually does it quite well.
Final Fantasy X-2 Opening Movie Real Emotion - YouTube
I DON'T KNOW WHY I LIKE THIS SO MUCH
Go on guys, what are your musical guilty pleasures?