CSI: Miami

Horatio Caine uses a Beretta Cougar in the first seasons, but later switches to a Sig Sauer P229 in 9mm pistol, as evident in "Lost Son," and again when it is mentioned in season three that 9mm guns are department issued. (It is unclear, then, how Calliegh can use a .45 ACP Kimber, but she does.) He also owns a Beretta 92, as seen in episode "Cyber-lebrity" and is given a Browning Hi-Power in .40 SW, as seen in "Ambush" and "All In". In one episode (Going, Going, Gone) he uses a Heckler & Koch G3-variant police-issue sniper rifle.

Calliegh Duquesne uses a Smith & Wesson 3913 "Ladysmith" Season 1-4 and a Kimber TLE Pro carry season 5 & 6.

Eric Delko uses a Heckler & Koch USP as his 9mm weapon of choice then switches to a Sig Sauer P226 Elite in 9mm (season 5)

Past character Tim "Speed" Speedle used a Magnum Research Baby Eagle/Jericho 941 in at least one episode (S1E18 "Dispo Day")

Ryan Wolfe uses a Beretta 92 Elite II as his compulsively cleaned duty weapon

Frank Tripp packs a Sig Sauer P226

Natalia Boa Vista finally acquires a Glock 26 9mm in season six as her carry weapon

In the season 6 finale, Kyle, Caine's son, is seen checking and loading a Smith & Wesson 4046 compact pistol in .40 SW

Glock, Smith & Wesson, Colt, Beretta, and especially SigArms weapons are very common in the hands of minor and side characters and villains throughout the series.

By far throughout the show the most seen gun, used by CSIs, criminals, and other characters is the M1911 pistol series.