Didn't have anything super specific in mind, but you could have things like:
- Stun gun (disable enemy but not permanently)
- Single use "hack", flick a switch from a distance once
- Grenade (area kill)
- Flash bang (perhaps makes an enemy fire wildly in a pseudo random fashion)
- Short term invisibility
etc etc. Not sure exactly what is and is not suitable for the vibes of your game - just strikes me that there are lots of things like this you could add in a full version