Miles Slater uses a pistol gripped Remington 870 shotgun during the Strip club massacre. A similar weapon is used by Yuri Petrov (Scott Adkins) during the fight at the church were it is later picked up by Father MacAvoy (Robert Carlyle).
Similar to the weapons used in Universal Soldier: Regeneration and Echelon Conspiracy Asaf Sadique uses a Bulgarian Arsenal AR which has been mocked up to resemble an M-16. The use of these mock ups is becoming more prevalent as more movies are filmed in the eastern bloc and, as in this film's case, most of the budget is spent on the actors.
Walther P99
A silenced Walther P99 is used by Lai Lai Zhen (Kelly Hu) when she's in the Hotel. She used the P99 without a silencer, when she killed Lina Sophia (the girl who tried to hit her with a car), and also during her fight against Anton Bogart.
Steyr SSG 69
Anton Bogart (Sebastien Foucan the acrobatic bomb maker from Casino Royale, and the founder of parcour along with David Belle) uses a Steyr SSG 69 (not a Remington 700) that he commandeers from another assassin to hit his first target in one of the first on screen kills of the movie.
Mini Uzi
The Mini Uzi used by a guy in the pub's massacre scene.
FN Browning
The gun used by an assassin during the montage of fallen competitors.
M72 LAW
Carl 'Longshot' Topuzov uses an M72 LAW to kill an assassin in a trailer and to attempt to kill Lai Lai Zhen and Father MacAvoy.
Compact Berretta 92
Harlow kills an assassin at the end of the firs tournament at the films beginning with a compact Berretta pistol. It is unknown whether it is the Berretta 92FS compact or the Berretta Centurion.
Sawn-off Double Barrel Shotgun
An assassin attempts to shoot Father MacAvoy, thinking he is one of the competitors, with a hammerless sawn-off double barrel shotgun.
Beretta 92FS
Beretta 92FS pistols are commonly used by the competitors in the film. Miles Slade uses a 92FS to shoot a stray dog, the female assassin who attempts to run over Lai Lai Zhen and Father MacAvoy attempts to use one on the Father when he tries to help her out of her overturned car, and many of the assassins in the fight at the Strip club are armed with Beretta pistols.
Unknown Pistol
During the fight at the Church, Yuri Petrov draws an unknown pistol on Lai Lai Zhen who quickly disarms him.
Heckler & Koch MP5
Heckler & Koch MP5 submachine guns can be seen in the hands of an assassin disguised as a police officer who threatens Lai Lai Zhen and Father MacAvoy and being used by an assassin during the montage of competitors being killed.
Browning BDA
A pair of Browning BDA pistols are used by Anton Bogart (Sebastien Foucan) during his attacks on Lai Lai Zhen and Father MacAvoy.
Arsenal Shipka
An Arsenal Shipka submachine gun is used by an assassin during the Strip Club massacre scene.
Walther PPK
A suppressed Walther PPK is used by an assassin attempting to kill Harlow in a parking garage.
Glock 17
During a montage of assassins being killed, an unseen assassin can be viewed firing a supressed Glock 17.
Arsenal AR-F
Duing the Strip Bar massacre, an assassin can be seen wildly firing an Arsenal AR-F.
RGD-5 Hand Grenade
During the fight at the Church, Yuri Petrov uses several RGD-5 grenades to attempt to kill Lai Lai Zhen (Kelly Hu).