Brentalfloss' stuff is pretty funny. (an early example:
http://www.youtube.com/watch?v=t8NsnLfIAcs&feature=channel)
Megadriver stuff is okay, but sometimes seems a little too heavy, (they mainly do heavy metal covers of sega tunes), but their stuff is free (last time I looked), so you can't complain.
TheOneUps are very good in my opinion. I love to relax to koopa beach.
http://www.youtube.com/watch?v=sJ6PmvwbJMY As for the konami kode, I haven't listened to any of their stuff, (except the collaboration that they did with Brentalfloss for his cd.)
A good idea would be to search em up on youtube.
also, these are only a few examples. there are loads more if you look for them.
(oh another example:
http://www.youtube.com/watch?v=6doJ0ErfSHg&feature=related Powerglove)