1:
Modes.
Endless arena mode.
Challenge mode. e.g. try to defeat those 5 super-deadly-spinning robot balls in 2 minutes.. idunno, something like that.
2:
Weapons.
Emp grenades? Energy guns? Any other energy based weapon.
3:
Skills.
Magnetism:
Pick up sliced bits of your opponents and shoot them back like shrapnel. High velocity, low penetration/damage, high or medium reload speed.
Spin:
You spin your sword/hammer/bow(?) and kill things. :I
Healing(or some sort of):
Pick up lying robot parts of your dead opponets and attach those to your clone drone, heal yourself! yay! Only 1 use per level.
Baddass selfdestruction:
If you have already purchased a clone, you can blow your self, make a big explosion, kill lotsa robots, yay. You cant buy another clone within 2-4 levels after B.A.S.D.
Maybe more ideas later, thanks for checking out this ones :D