[@MetalLover]Did you read the discussion we had about railguns?
Since they could be very much a future plausibility would you allow hand-carried railguns?
They would be potentially better than standard guns but far from as OP as they are presented in games and movies.
Basically think of an alternative to firearms. Both having their advantages and disadvantages.
There are already existing and real concepts to solve the issue with having a sufficiently compact power source.

Basically think of a different assault rifle or sniper gun and that's pretty much what a railgun are.