So, this is a small list of things that I think should be added or changed:
UPGRADES IN TWITCH MODE: in twitch mode, viewer can give the streamer upgrade points
PICK YOUR POISON: just allows the player to pick their starting weapon in story or endless mode. (ex. starting with a hammer instead of sword)
SHOCK WAVE: I've noticed that the hammer isn't what it's cracked up to be, so maybe the hammer creates a small shock wave when it smacks into the ground. This knocks enemies down like a spider-tron bomb. This shock wave would grow more powerful the bigger the hammer is.
FLAME KICK: Sets the kicked enemy on fire
ONE LEG CHALLENGE: Player has to complete 10 levels with one leg