I've got a boss idea: Meta Knight (from the Kirby Series).
It would have 5000 HP;
a fast playertype;
and the Galaxia, a sword that can deal high damage (use Takato 14's Galaxia from the sword pack or make your own) in a very fast time (5 hits per second, 10 damage per hit) as it's only weapon.
I got another idea for a boss (even though it's not as good as the other): Nitramj
It would have very low HP (as much as Mocheeze or even less);
a fast player type;
and Bushido's Homing Vector, a weapon that shoots 7 Homing Lasers, which all go on a player and kill them automatically in one hit, without the possibility to be dodged, as it's only weapon.