In real life most guns being fired are predominantly just extremely loud to the firer, so I dont think I'd be able to call a gun that I'd find satisfying to hear myself shoot. OR a 1911. Love those things. I'd probably say a bow makes the most satisfying sound to fire. Different types make different sounds, and I like all of them. As far as guns other people are shooting though, I like the sales pitch video of the NTW-20 thats out there somewhere. There is nothing at all un-satisfying about the NTW-20.
Game wise, probably the Spas 12 in L4D2. It's a very uncompromising sound.