luiginumberone

Best answer as chosen by Asker / Ratings
This is already on this web site in several places. Rather than re-list them all, I'll post the links so you can look for yourself.
Next time, please check the "Cheats" and "User Submitted Cheats" pages before asking a question, just to make sure it's not already answered.

Http://www.supercheats.com/guides/mario-kart-wii/
Http://www.supercheats.com/wii/mariokartwiicheatcodes.htm
Http://www.supercheats.com/wii/mariokartwiicheats.htm