The spectacularly-bearded Smooth McGroove has an impressive knack for rearranging well-known video game themes in a capella, using only his voice and his cat. He picked a really good one in his latest video, the Spark Mandrill theme from Mega Man X.
You gotta love this guy's taste in video game music. His YouTube channel is filled with other really great remakes. Here's a few that we liked the most:
The battle theme from Final Fantasy VII
Bloody Tears from the Castlevania series
To Zanarkand from Final Fantasy X
Oh, and this one is not from a video game, but still worth sharing, because it's too amazing:
Megaman X - Spark Mandrill Acapella [YouTube]