Florida Department of Law Enforcement (FDLE) Detective Jim Longworth (Matt Passmore) carries a Smith & Wesson 4506 as his main sidearm. He uses it in the pilot episode to kill a Caiman that had eaten the head of a murder victim. In "Mucked Up" (S1E04), Longworth is seen practicing with his pistol, firing at an empty milk jug floating in a pond and then teaches Jeff Cargill (Uriah Shelton) how to shoot the weapon, giving him a second empty milk jug to fire at. The first few shots fall short, but he finally hits it, much to his excitement.
In "Pilot" (S1E01), Detective Longworth's partner Mike Ogletree (John Carroll Lynch) can be seen holding Longworth at gunpoint with what appears to be a Smith & Wesson Model 627.
Heckler & Koch P7
A Heckler & Koch P7 is found by Jim in "Bird in the Hand" (S1E02). It's identified as an "HK P7".
Colt M1911A1
In "Doppleganger" (S1E06), Michael Nelson (Dean Norris) is seen pulling an M1911A1 on Jim.
SIG-Sauer P230
In "A Perfect Storm" (S1E03), a murder suspect named Tommy Owens (Rick Robinson Jr.) can be seen armed with a SIG-Sauer P230, holding it on a woman and threatening to kill her when Longworth arrives. Longworth distracts Owens with prescription medication he had been denied then rushes him. The suspect fires the pistol as Longworth tackles him, but the shot goes wide and misses hitting anyone.
Glock 17
The Glock 17 appears in the series as the primary sidearm of police officers and State Troopers in most episodes. A Glock 17 is also carried by Longworth's supervisor, Colleen Manus (Michelle Hurd).
Glock 26
Colleen Manus (Michelle Hurd) carries a Glock 26 beginning in Season 2. Illinois Det. Sam Harper (Jim's former partner from Chicago) carries a Glock Compact, probably a Glock 26, in the episode Old Ghosts.
Submachine Guns
Heckler & Koch MP5A3
In "Pilot" (S1E01), a SWAT officer can be seen armed with a Heckler & Koch MP5A3 with Surefire dedicated forend weaponlight when arresting Ogletree.
Rifles
M4A1 Carbine
In the pilot episode, at least 2 SWAT officers can be seen armed with M4A1 carbines fitted with M68 Aimpoint red dot scopes, Surefire Universal weaponlights, and RIS foregrips during Ogletree's arrest.
Other
"Bang Stick"
In Season 1's finale "Breaking 80" (S1E13), Kim Nichols (Julie Gonzalo) threatens a man with a "Bang Stick", described earlier in the episode as firing light .44 loads to scare away alligators.