No weapons, only tools
Everyone has an idea for a marine weapon they'd like to see, but what about equipment for the rines to use?
Personally I would like to see some medical supplies, some small traps to close off vents (as an alternative to mines), extra ammo to drop for teammates, an ammunition backpack, perhaps something to run faster or something. Basically lot of ways to tweak your playstyle with some disposable p res. Note none of these do damage (except for the traps.)