If you're playing on PC, 10mm and revolver (with explosive upgrade) are the two best weapons. I'd think it would be a little harder to aim on console so the autos and shotguns are probably more useful. The same can be said for any game where you fight various enemies who tend to be stationary (or maybe occasionally moving) while in combat. If you play GTA, Mafia 2, or whatever, on PC, it's pretty much headshot city. Either way, the upgrades you can put onto the sidearms make them extremely deadly. Hiding behind cover, popping out and headshoting your enemies is probably the easiest way to dominate in the game.