I've gotta have the Terrible Shotgun and the Plasma Rifle.
Combat Knife, silenced 10mm, gauss rifle, laser pistol. Frag grenades when my enemies won't follow my instructions for placement.
Non-vanilla, it changes dramatically, however. m72 and ppk12 backed up by the combat knife.
Why does combat knife never leave my lineup? Because I was able to gut a supermutant overlord with one before he could do signifigant damage to me. It hurts, it doesn't wear down as quickly as most weapons seem to, and it's FAST.