For personal weaponry you cannot beat the chemical projectile. All the power needed to incapacitate in one small brass shell. It contains the energy needed and when ejected takes all the waste heat with it. No need for batteries. No worrying about em interference. Nothing that can't be constructed by nanofabrication with a few simple universally available elements.
The bullet of the 30th century is still recognizable to a 21st century human but innovation has not passed it by. A standard commonwealth rifle round is 6mm of brass jacketed lead. The round is tipped with a nano-diamond, a superhard fullerite, the hardest substance known to sophonts. This nanodiamond allows the round to penetrate fullerene and graphene armor common to the battlefield of 3025.