Luigi, for the same reasons as will, only supplanting Mario Kart for Mario Tennis. (He has minimal traction in both games.)
I also have a close affinity for Ludwig von Koopa, one of the seven offspring of the Koopa King Bowser, of SMW/3 fame.
Fun Linkage:
Mario Monsters
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click to show Ludwig Von Koopa is a very, very smart Koopaling, and he's also the oldest. Ludwig enjoys designing some really tough machines, but rarely seems to build any. His hair is completely blue and he wears a green shell. Despite Ludwig being very smart, his nickname is Kooky. Where these names came from I will never know � maybe it's due to his crazy looking hair. Ludwig is also a bit of a gentleman, he enjoys listening to a bit of opera in his spare time, as geniuses (albeit sometimes evil ones) often do! Although his full name is Ludwig von Koopa, most people just call him Ludwig. In Super Mario Bros. 3 Ludwig is the seventh boss and in Super Mario World, Ludwig is the fourth boss.