The sidearm of choice for Michael Westen (Jeffrey Donovan) continues to be the SIG-Sauer P228 at the beginning of Season 4.
SIG-Sauer P226 (Nickel)
A nickel SIG-Sauer P226 is the sidearm of choice for fellow burned spy Jesse Porter (Coby Bell). He holds the SIG on Fiona in Season 4's "Blind Spot" and uses it throughout the Season 4 finale "Last Stand" (S4E18).
SIG-Sauer P226
In Season 4's "Past & Future Tense", former spy Paul Anderson (Burt Reynolds) uses the SIG-Sauer as his sidearm of choice. In Season 4's "Dead or Alive", corrupt detective Pete Jackman (Raphael Sbarge) also carries a SIG-Sauer P226 and pulls it on Michael.
Beretta 92FS
Sam Axe (Bruce Campbell) carries a Beretta 92FS as his personal sidearm throughout the series. The Beretta has also seen use by various other characters throughout the series' run, in both suppressed and unsuppressed forms.
Beretta 92FS Inox
The Beretta 92FS Inox is used by con artist Nick Madison (Clayton Rohner) during a hostage situation in Season 4's "Breach of Faith". Michael later is seen with the handgun.
Colt M1911 Series
Colt 1911 series handguns are seen numerous times throughout the series.
Colt Compact M1991A1
In Season 4's "Hot Property" (S4E14), a Colt Compact M1991A1 is carried by Fiona that later ends up in the hands of the thief Natalie Rice (Callie Thorne), who attaches a suppressor to it.
Glock 17
Glock 17's are used by Miami PD in the many instances when Mike tricks criminals into being arrested to solve his problem of the week.
Glock 26
Throughout Season 4, Fiona carries the Glock 26 as her preferred sidearm.
The Heckler & Koch P30 is Michael's new sidearm beginning in Season 4's "Center of the Storm". In this episode, Cole (Jon Seda) is seen pulling a Heckler & Koch P30 after disposing of Michael's P228. Cole uses the P30 throughout the episode to threaten Michael as well as combat Matt Reece's thugs. At the end of this episode he gives it to Michael. From this point on in the show, it becomes Michael's sidearm.
Heckler & Koch P2000
In Season 4's "Past & Future Tense", Vitali (V.J. Foster) carries a Heckler & Koch P2000. Michael is later seen with the handgun.
Heckler & Koch VP70
In Season 4's "Brotherly Love", Michael hands off a Heckler & Koch VP70 to Sam that he says Fiona modified to fire three-round bursts.
Jericho 941FB Compact
In "Where There's Smoke" (S4E08), Jacob's brother Eddy carries a Jericho 941FB Compact as his sidearm and is seen pulling it on Michael.
Smith & Wesson SW99
In "Fast Friends" (S4E02), Ming Khan (Byron Mann) carries a Smith & Wesson SW99 with a nickel-plated slide as his sidearm.
Smith & Wesson 4506
In Season 4's premiere "Friends and Enemies" (S4E01), a Smith & Wesson 4506-1 .45ACP pistol appears to be the handgun carried by the biker named Hunter (Andy Mackenzie).
Smith & Wesson 945PC
In Season 4's premiere "Friends and Enemies" (S4E01), Big Ed (Andrew Bryniarski) is armed with what appears to be a Smith & Wesson 945 Performance Center.
In "Made Man" (S4E03), mobster Tony Caro (Nestor Serrano) is seen pulling out a 4" Smith & Wesson Model 500 and placing on a table when threatening Michael.
Smith & Wesson Model 686
Fiona disarms a parking lot attendant of his 686 in Season 4's "Guilty as Charged" (S4E12).
Taurus Model 85
Fiona Glenanne (Gabrielle Anwar) twists the cylinder of her stainless Taurus Model 85 next to Mike's ear at the beginning of Season 4's "Hard Time".
In Season 4's premiere "Friends and Enemies" (S4E01), both Michael and Vaughn (Robert Wisdom) are seen carrying Heckler & Koch MP5A2's fitted with a scope on a mission to find an illegal gunrunner.
Heckler & Koch UMP
The Heckler & Koch UMP is used by several of Vaughn's men in Season 4's "Guilty as Charged" (S4E12).
Ingram MAC-10
In Season 4's premiere "Friends and Enemies" (S4E01), Fiona is seen loading a few MAC-10's before going to see a client. Later in the episode, Michael also wields two MAC-10's to try and intimidate a biker gang.
Mini Uzi
In "Where There's Smoke" (S4E08), One of Jacob's thugs carries a Mini Uzi during the kidnapping attempt. Michael is later seen with the SMG.
Shotguns
Mossberg 500 Cruiser
In "Center of the Storm" (S4E09), Michael takes a Mossberg 500 Cruiser off a witness and then uses it to detonate an explosive improvised out of an air conditioner.
Mossberg 500 Cruiser (Foregrip and saddle shell holder)
A Mossberg 500 Cruiser fitted with a foregrip and saddle shell holder is a frequently used shotgun in the series.
Mossberg 500 Persuader (Folding Stock and Door Breaching Brake)
A frequent shotgun seen used in the series is a Mossberg 500 Persuader fitted with a police folding stock, saddle shell holder, and door breaching brake.
Remington 870 Folding Stock
A Remington 870 with a folding stock is used by Fiona on several occasions.
Saiga 12K
In Season 4's "Center of the Storm" (S4E09), a modified Saiga 12K automatic shotgun is said to have been used in an attempted hit on an FBI witness.
Serbu Super Shorty
In "Brotherly Love" (S04E15), Nate Westen (Seth Peterson) uses the Serbu Super Shorty during a raid on Buckwild's chop shop.
Assault Rifles
Colt Model 933
In Season 4's "Breach of Faith", Miamo Metro SWAT officers are armed with the Colt Model 933.
Heckler & Koch HK416
One of the frequent weapons used by Jesse Porter (Coby Bell) in Season 4 is the Heckler & Koch HK416. In Season 4's "Fast Friends", Jesse storms a gangster's compound armed with the rifle. In Season 4's "Guilty as Charged", Jesse uses the Heckler & Koch HK416 to shoot Michael.
An M16A2 is briefly seen in the hands of a Miami Metro Police officer during the standoff in Season 4's "Breach of Faith" (S4E4).
Norinco Type-56
A rack of Norinco Type 56 rifles are seen in Season 4's premiere.
SCAR-L
The FN SCAR-L is carried by Matt Reece's thugs in Season 4's "Center of the Storm". It's used when when Michael beats down the thug, causing the weapon to go flying in the air.
SIG SG 552
The SIG SG 552 assault rifle is a frequently used weapon in the series. The rifle is used by one of Matt Reece's thugs and Matt Reece himself in Season 4's "Center of the Storm." In Season 4's "Guilty as Charged", the SIG rifles are used by Fiona and Sam throughout the episode.
Sniper Rifles
Heckler & Koch SL8-1
The H&K SL8-1 is used in several episodes. In Season 4's "Made Man" (S4E3), Michael uses a suppressed SL8-1 to shoot out the security guard's tires. Later, Michael and Fiona use 2 suppressed SL8-1s to shoot Gio's engine block. An SL8-1 is also used by Sam while providing cover for Michael in Season 4's "Dead or Alive" and is fitted with a laser sight and suppressor in Season 4's "Out of the Fire".
Remington 700 AICS
A Remington 700 AICS is used by Sam as he provides cover in Season 4's "Guilty as Charged".
Winchester Model 70
A Winchester Model 70 is frequently used by Sam to cover Mike or to provide distractions.
Heavy Weapons
Barrett M107
In Season 4's "Fast Friends", Barrett rifles are among the weapons supplied by Michael to Ming Khan.
M136 AT4
In Season 4's premiere "Friends and Enemies" (S4E01), an M136 AT4 is among the weapons seized by Vaughn (Robert Wisdom) when on a mission to find an illegal gunrunner.
Ramo RT-37
What appears to be the heavily-modified Ramo RT-37 riot control launcher used in the Transformers films is first seen among the weapons supplied by Michael to some gangsters in Season 4's "Fast Friends" (S4E02). The launcher, fitted with a red dot sight (appears to be a Bushnell Holosight) and M4 type stock, is also used by Jesse Porter (Coby Bell) in Season 4's "Neighborhood Watch" (S4E05).
Fictional Gatling Gun
A CGI-created eight-barreled Gatling Gun is seen firing from underneath an MQ-1 Predator UAV in order to assassinate a rogue arms dealer (Michael Ironside) in Season 4's "Friends and Enemies".