The Mauser Karabiner 98 (98K) was the standard weapon for all German ground forces during World War 2.
Lee-Enfield No 4 Mk 1*
Used by all British Troops, mostly the Grenadier Guards in the Armored Column as well as the British 1st Airborne Division when they were trapped in Arnhem. The No 4 Mk 1* rifle was also seen in the hands of the Polish Airborne brigade troops. Colonel John Frost (Anthony Hopkins) was also seen using a No.4 rifle during the later stages of the battle for Arnhem.
M1 Garand
Used by American troops.
M1 Carbine
Used by American Soldiers and mounted on jeeps and other vehicles. Most notably seen when James Caan pulls one out of it's Jeep mount when he is hiding from a German Patrol in the Forest. Also used by Elliott Gould when leading the charge to capture a bridge.
M1A1 Paratrooper Carbine
A Folding stock version of the M1 Carbine, this should have been more prevalent amongst the American Airborne troops, however only a few samples are ever seen in the film, most notably during large scenes of massing troops.
M1911A1
Used throughout the movie, especially by James Caan when threatening a 101st Airborne combat surgeon (Arthur Hill) in order to get him to treat his wounded captain (Nicholas Campbell). The handgun is also seen, albeit briefly, holstered amongst American officers, NCOs and Military Police.
M1911
Apparently, the widespread issue of Browning Hi Power pistols (the iconic handgun of elite British Military units in World War II) to British Airborne units, only started after Operation Market Garden, so it is appropriate that they are seen using another handgun. A likely candidate in this case is the M1911 chambered in .455 Webley, issued to members of the R.A.F. In the film, the British M1911 is used by Roy Urquhart and several other Airborne officers as they try to evade capture by Waffen SS forces.
M1A1 Thompson
Seen only briefly during some of the massing troops scenes, the M1/M1A1 Thompson has a peculiarly small roll in the film. The vast majority of Americans are armed with M1 Garands and M1 Carbines, which is unusual, since during many of the battles, nary an M1A1 Thompson can be seen, which is inaccurate.
Browning Automatic Rifle
Browning M2 HB
Used by British Armored troops mounted to their Lend Lease Sherman Tanks.
Sten Mk5
The standard submachine gun for British and Polish Airborne units. Differentiated from earlier models by the wooden vertical foregrip and wooden stock.
No2 Portable Flamethrower
Used in the attack on the German bunker on the Arnhem bridge this weapon, known as the "Lifebuoy" for its' resemblance to a lifesaver, was the standard British flamethrower.
PIAT
Projectile Infantry Anti-Tank
Used throughout the movie by British and Polish airborne units (who were similarly equipped) this weapon fired a 3 lb. hollow charge warhead via means of a powerful spring which ignited its propellant. The weapon had a powerful recoil which necessitated it being fired prone since any other position would knock the user flat down. Seen especially during the repulse of the initial German assault on the Arnhem bridge.
Bren gun
Vickers Machine Gun
Used by British soldiers when the armored convoy is ambushed.
Karabiner 98 Sniper
Used by designated Marksmen and Snipers in the German Armed forces.
MP40
Used by German troops.
MG42
Used by German troops
MG34
The most commonly seen MG used by German troops in the film.