Colonel Von Horst (Warren Clarke) uses a Walther P38 to threaten Nick after he smarts-off in German. Sergeant Kruger (Jack Cooper) also uses one to shoot an informant later.
Chocolate Mousse's (Eddie Tagoe) weapon is an M1928 Thompson. During one scene, Chocolate Mousse "loads" his weapon like a musket, even pouring gunpowder and using a ramrod.
MP40
The MP40 is seen quite frequently in the hands of the East Germans and the French Resistance.
Sten Mk II
Karabiner 98k
The Karabiner 98k can be seen in the hands of the East Germans.
M1 Garand
Deja Vu uses an M1 Garand. Also, in when the East Germans attack the Resistance headquarters, a German soldier, for some reason, is using an M1 Garand.
M1 Carbine
An M1 Carbine can be seen in the hands of at least one of the French Resistance fighters.
MG34
An MG34 is seen mounted on an East German car that chases the heroes after they rescue Hillary's father from Flergendorf Prison.
Miscellaneous Shotguns
During the "Skeet Surfin'" scene near the beginning of the movie, the surfers can be seen with a variety of shotguns.
SIG P210
During the shootout at the farm between the Resistance members and East German troops, Nick Rivers is given a SIG P210 to use against the Germans.
Enfield No.4 Mk.1
Unknown automatics
The gun in this picture looks to me like a Beretta 92F, however the film is set around WWII and the 92F was not designed until 1972 so it could just be a movie mistake and they were not careful to use guns and other weapons from that era.
It's set in the 1950's. Still too early for such a gun, but then again, they also have a 1970's Ford Pinto and overall intentional flagrant disregard for period authenticity anyway.
Unknown revolvers
Cannon
Chocolate Mousse (Eddie Tagoe) uses a muzzle-loading field cannon during the attack on the French Resistance's headquarters.