Handguns
Pistol
The Pistol has been seen in the first trailer. It also appeared in games including GTA IV, GTA Chinatown Wars and GTA V.
Rockstar has not shared more about the Pistol yet. This page grows as new trailers and screenshots come out.
More handguns
Capo pistol
Seen in official screenshots.
ES9
Seen in the Ultimate Edition screenshots.
K17
Seen in the Ultimate Edition screenshots.
Morgan
Ultimate Edition
Seen in the Ultimate Edition screenshots.
Mustang .357
Seen in official screenshots.
Nipper .38
Seen in official artwork.