I'm not usually attracted to slash-em-up fighting adventure games unless they have a good dose of stealth involved, in which case, they're really not slash-em-up, are they?
That being said, mine eyes cannot get enough of Madworld, a highly stylized game coming out for the Wii sometime in 2009 (Q1 for now, but we'll see what happens).
For more details on the game, head over here