The following weapons were used in the film Guadalcanal Diary:
The M1928A1 Thompson is the main weapon of Captains Cross (Roy Roberts) and Davis (Richard Conte), some of the Marines, and is used by some of the IJA (instead the correct MP18, the MP28/II, or the Type 100).
A Marine can be seen with a Reising M50 when they land on Guadalcanal.
A Reising M55 can be seen hung on a Marine's bed below deck.
M1903 Springfield Mk 1
A Marine can be seen with a Springfield M1903 Mk 1.
The M1903A3 Springfield is correctly depicted the standard issue rifle of the United States Marines (as they did not get M1 Garands until the end of 1942). US Army soldiers and IJA soldiers use them as well (the later using them as a stand in for the Arisaka Type 38 and the Arisaka Type 99).
F4F Wildcats which typically mount Browning AN/M2s are seen in actual war footage.
During the final push Marines are seen carrying Browning M1917s.
Browning M1919A4s are carried by Marines and mounted on boats and M3 Stuart tanks.
The Aircraft version of the Lewis Gun is used by IJA forces. This is somewhat correct as they were issued to the Imperial Navy instead of the Army under the designation "Type 92" however those Lewis Guns had a much larger drum magazine, used in a flexible mount, and had a distinctive trigger guard.
US Marines use M1 Mortars to provide supporting fire.
IJA soldiers use M2 Mortars to keep the Marines back.
Mk 2 Grenade
Mk 2 hand grenades are used to blow up Japanese MG nest.
TNT is also used to to blow up Japanese MG nest.