Seems to be the standard pistol throughout the game. From the gameplay I saw, it shows Joe giving himself and Vito a Colt M1911 but with a large magazine. This weapon is seen being used by Vito, Joe and Henry throughout the game. The gun in the game is actually an M1911, close inspection of the backstrap shows that it is flat and not rounded.
The Main Submachine Gun of gangsters.The Thompson M1928 commonly seen with a 50 round drum. The gameplay video shows it being almost uncontrollable, this is probably because the game has no lock on system. Whenever your in the Drivers seat and your chasing someone, Joe will use this weapon until it runs out. When Henry is shot in the leg, Joe uses a Thompson to kill the man with Vito. Recently in a new trailer, the original thompson was seen. Rhe 1928 Thompson in this game is a "franken-gun" of sort, having some features of both the 1928/A1 and the M1/A1 models. The gun in Mafia II has the M1 style stock, the M1 style bolt, The receiver of the M1, and although this is not the case with either weapon,it fires from a closed bolt
Vito Scaletta is seen holding an MG42 in the gun shop screen. In a trailer we see the man with an eye patch is seen holding this. Vito is then seen firing it into the fat mans car until it explodes.