cyberlimbs
Over shield arm
add a cyber arm that when used gives you an extra layer of protection. the details would ultimately be the creators choice, maybe have something the reduces bullet penetration/damage by a small percentage but have that percentage scaled with the rarity of the limb that provides it. (surviving a kestrel headshot with 1hp would be crazy in my opinion) or just flatout add one that gives you extra hit points. picture the way the overshield in arc raiders words for a better idea of how the shield would work
name to be determined
maybe an arm that you can use multiple times that sort've shoots out a lot of force that can be used to lauch players in the direction you point it or can launch you in the air when pointed at the ground
mobility denial system or MDS (a tool used by the U.S. military)
an arm that instead of shooting sticky goo shoots a slippery goo that will make traction and movement slightly more difficult but doesn't cripple the player its used on as much as the slugger does
A Flamethrower
it would be a flame thrower... pretty self explanatory... but the tank would run out rather quick as it would only be as big as maybe a bicep
Name to be determined
an arm that pops up some sort of EMS system that temporarily disables or scrambles the opponents maps and minimaps in the surrounding area it is applied.
laser pointer
A laser arm that does a small constant amount of damage to oponents shields. the better your aim the more effective it is.
more suggestions
portal gun arm
Legs
add a pair of legs that allow you to run up walls using some sort of suction or friction. and when you jump off a wall you jump upward diagonally ultimately making it easier for newbies to use their jetpack.
sort of like how wall jumping in cod would work
i can't think of leg abilities...