Lee-Enfield SMLE's are used by the Arabs and British throughout the movie. Turkish soldiers also (incorrectly) use these weapons in several scenes, interchanging with Mausers, presumably depending on what country the scenes were shot in (Jordan, Spain or Morocco) and the availability of the rifles.
Gewehr 98
The Turkish army uses the Gewehr 98 rifle in the movie interchangeble with the Lee-Enfield SMLE.
Browning M1919
Browning M1919's are seen used by the Turks in the first train attack scene. This is an anachronism since the movie takes place from 1916 to 1918.
Sea Battery
Lawrence and the Arabs conquer Aqaba to eliminate the threat to supply ships, that the sea batterys possesses.
Vickers Gun
The Arabs use the Vickers Gun when they assault the trains. Lawrence incorrectly identifies them as Lewis Guns earlier in the film.
Flare Gun
Lawrence and Col. Harry Brighton both use a Flare gun over the course of the movie.
Mauser C96
The Weapon used by the Turkish soldier to shoot Lawrence is a German Mauser C96. These guns can be seen in several other scenes, including Jose Ferrer's Turkish Bey in the Deraa sequence, though several Turkish officers during the attack on Aqaba can be seen using unidentified revolvers.
Howitzer
The retreating Turkish column tow a Howitzer along with them.
M1914 Hotchkiss
The Turks are seen deploying a French M1914 Hotchkiss machine gun when Lawrence and the Arabs attack the retreating Turk column.
Jezail
Several of Lawrence's bodyguards towards the end of the film are armed with some type of Jezail, a commonly used matchlock musket (notable for its rounded, forked stock and long barrel) found in the Middle East.