Here are some suggestions. When killed, they robots drop ammo. The crabs drop rifle ammo, the small ones drop revolver ammo, the big ones drop shotgun ammo, and the bomb ones drop rocket launcher ammo.
Make a "god mode" option in the menu. Infinite ammo, health, and time stop is a toggle, not an ability.
Add a thruster movement option, its like the dash, but has a longer cooldown and can be used in all directions. Also its sends you further than the dash.
These are just suggestions