Level select cheat:
 
 D-L-D-R-D-U (D=down, L=left, R=right, U=up)
 
 do this at the menu screen and you'll see all the levels pop-up
 
 There's some in game cheats, but I couldn't find what all of them did.
 All the cheats are Up-Up-Up and then a combination of Slash, Block
 and Jab.
 
 I think the most useful is uuubbb which moves your strength and
 endurance meter up a notch.