typically at low levels you'll do fine with rageclaws or kuthrik claws. however, if you want some serious cheese, bind the threefold mask of the chimera to your totem chakra - it allows three bite attacks at no penalty to multiple natural attacks, and all with full strength. it can get pretty brutal quite quickly.
personally, i'd take a single level in barbarian, and then take the cobalt rage feat for a nice boost to damage and will saves while raging. i almost consider this to be mandatory.
at low levels, they'll really shine and almost seem to make the other melee characters obsolete.