I am assuming the same, either the glock, the 92f or a gun very similar to the USP, but coming to think of it, the glock has been one of the most used guns on gta games, not only that, but law enforcement seems to use it as well, although it seems like the 92f is more of a preferred options for LAPD (lspd in this case)
The glock has been used in GTA LCS and GTA4, how can it be most used? The most used is sure as hell the Sig p226/m1911, not sure witch one cuz the gun has 17 rounds. It has been in GTA3, GTA VC, GTA SA.