Game mode ideas: HK FFA, Nades out.

hard core FFA
info: everyone starts with a sidekick and nothing else. on the map is only equipment power ups, drop walls, grapple hooks, repulsers, overshields, and cloaks.
gameplay: First to 20 kills wins. The catch, no one respawns until it is down to the last 2 players.

Nades out
info: you have your fists and a bag of frags. Infinite frag grenades but on a cool down.
on map items: repulsers, grapple hooks, drop walls and different grenade types. You only have infinite frags.