Jack Bauer (Kiefer Sutherland) uses a Heckler & Koch USP Compact, chambered in 9x19mm Parabellum, throughout episodes 5-24
of Season 4, in both sound suppressed and unsuppressed form.
TRIVIA: There were only two H&K USP Compacts used by Kiefer Sutherland through the entire run of the series. This was because Kiefer is a method actor and did not like to change props. He only wore 3 real kevlar bullet proof vests through out all 8 seasons. (IMFDB thanks The Golden Closet for providing the documentation on this gun.)
Head of Field Ops Ronnie Lobell (Shawn Doyle) uses the SIG Pro SP 2009. After he is killed in episode 2. Jack Bauer (Kiefer Sutherland) uses this weapon when staging a robbery in episode 3, and when he rescues Secretary of Defense Heller (William Devane) (At the end of episode 5). Also used by Secretary of Defense Heller when covering Jack during the rescue operation in episode 6. Also used by Tony Almeida after he is brought into CTU.
In the beginning of episode 1, an assassin on a dirt bike derails a train and shoots a briefcase handler with a suppressed Beretta 92FS and takes his briefcase in episode 1. Abdul Manesh (Matt Gallini) uses a suppressed Beretta 92FS when killing all of Andrew Paiges (Lukas Haas) co-workers in episode 1. LAPD officers approach Richard Heller (Logan Marshall-Green) with their standard issue Beretta 92FS in episode 2. Several assassins use suppressed Beretta 92FS's during the ambush at Felsted Security in episode 7. Also some suppressed 92FS's are captured and used by Jack when he's low on ammo in episode 7.
A CTU agent uses a Glock 19 at a dry cleaning store to capture Tomas Sherak (Faran Tahir) in episode 1. Jack Bauer (Kiefer Sutherland) also gets a Glock 19 after knocking out a CTU guard in episode 1. Omar (Tony Plana) also uses a Glock 19 when taking Audrey Raines (Kim Raver) hostage during Heller's rescue in episode 6. Tariq (Rene Millan) uses a suppressed Glock 19 to kill Behrooz Araz (Jonathan Ahdout) in episode 6.
During the kidnapping of Secretary of Defense James Heller (William Devane) two terrorist's with IMI Uzi's shoot several Secret Service agents trying to get Heller in episode 1. Several Uzi's are seen at Secretary Hellers Rescue by approximately 5 terrorist in episode 6.
A Steyr SPP (converted to automatic fire) was used in episode 1 by a kidnapper. A Steyr SPP is used in episode 6 by a terrorist at Secretary Heller holding location. One of the assassins uses a Steyr SPP during the ambush at Felsted Security in episode 7.
Jack Bauer (Kiefer Sutherland) uses a Accuracy International AWP to kill two terrorists before they kill Andrew Paige (Lukas Haas) in episode 3. In episode 8, a sniper on a roof shoots Henry Powell (Robertson Dean) in the chest and all that is seen is a straight rifle barrel. It could have been a Heckler & Koch PSG-1 because of the straight smooth barrel but is very unlikely because of how rare this weapon is seen in movies, so I identified it as a Accuracy International AWP.
Dina Araz (Shohreh Aghdashloo) asks her son Behrooz Araz (Jonathan Ahdout) to clean up his dirty mess by killing his girlfriend Debbie Pendleton (Leighton Meester) with a 3" stainless steel Smith & Wesson 686 in episode 4 & 5.
That's not a 686, it appears to be too small and it doesn't have a full length ejector shroud.
AKMS rifles are seen being wielded by terrorist in episodes 2, 4, and 6 so far. Secretary of Defense Heller (William Devane) himself kills 2 terrorists with one while trying to escape in episode 4.
Secretary of Defense James Heller (William Devane) was supposed to be executed with a Smith & Wesson 4506 but was interrupted and saved by Jack Bauer doing a rescue operation in episode 6.
US Marines use M4A1 Carbine's with Foregrips, M68 reflex sights, AN/PEQ2A Laser Aiming Modules, and Tactical Lights in episode 6. Also, Chloe O'Brian uses the M4A1 to defend herself against one of Marwan's hitmen in episode 19.
The Heckler & Koch MP5A2 is another weapon used by the CTU field ops team.
Heckler & Koch MP5A2's with Surefire 628 dedicated forend weaponlights can be seen in episode 7 at the CTU weapons center when Audrey and Jack are talking.
Jack gets a Glock 20 from another dead officer and after making a call, he hands it to Audrey telling her to space out her shots and conserve ammunition in episode 7. A closer look at the barrel looks like a 10mm Glock 20. It's also surprising that Audrey keeps her eyes open the whole time with out blinking.
The Glock 17 is seen by many CTU teams and terrorists. Navi Araz (Nestor Serrano) uses a sound suppressed 2nd Generation Glock 17 to hunt down his son and wife throughout episodes 8 and 10. Behrooz Araz (Jonathan Ahdout) gets a hold of the Glock 17 and kills his father in episode 10. Curtis Manning (Roger Cross) uses a 3rd Generation Glock 17 at his standard issue sidearm throughout the season. Habib Marwan (Arnold Vosloo) uses a 3rd Generation Glock 17 as his standard sidearm throughout the season. Also used by Tony when he arrives back at CTU after being held hostage by Mandy.
A Walther P99 is used by David Conlon when he attempts to kill Jack Bauer and Paul Raines. He succeeds in shooting Paul Raines in Episode 13 (7 p.m.-8p.m.).
Also used by Mandy in the final few episodes, most notably to kill Agent Castle.
