I never use sprayguns, due to the horrible accuracy... But on the other hand, I have used UAC Carbines from time to time as an accuracy training weapon. It has plentiful ammo, reasonable accuracy, and low damage (which is often handy for accuracy training). So I sometimes use it to show civilians or zombies. With any luck, the target doesn't die but falls unconscious (which then allows me to train bravery as well...)
... that said, if I'm actually trying to kill something, then it shotguns for close range or muskets for long range (in the very early game anyway).