Handguns
Morgan
Ultimate Edition
The Morgan has been seen in the Ultimate Edition screenshots. It is part of the GTA 6 Ultimate Edition.
Rockstar has not shared more about the Morgan 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.
Mustang .357
Seen in official screenshots.
Nipper .38
Seen in official artwork.
Pistol
Seen in the first trailer. Earlier in games including GTA IV, GTA Chinatown Wars and GTA V.