The Americans had many weapons during World War 2. The M1 Garand was carried by most rifle platoons and also in some machine gunner platoons even though it was a semi-automatic rifle. It carried an 8 round clip that you couldn't reload untill you heard the distinctive click that meant you need a new clip. The other popular semi-automatic rifle was the M1A1 Carbine. Unlike the M1 Garand this rifle could be reloaded whenever you needed and didn't ding. It was also very common in rifle platoons. The pistol that was carried by the Americans was the Colt 1911. Many people claim that this pistol was the best in the war. Its .45 rounds made it extremely dangerous when in close range. It had a very good grip and a upgradeable iron sight. The most common and accurate marksman rifle would be the Springfield 1903. It was one of the most accurate snipers rivaled only by the Kar-98 by the Germans. The .357 Magnum wasn't very accurate but it did pack a punch. The Grease Gun was used so often because of how cheap it was to make. It took two dollars to make. The only problem with this weapon is that it would jam sometimes. The Trench Shotgun was also deadly. If an American was captured with this weapon they were executed on spot because of how deadly it was. The M1A1 Flamethrower was used to clear out bunkers and trenches. It did its job extremely well especially in the Pacific Theater. It was useful there because it burned down vegetation that Banzai (Japanese troops that would charge American soldiers with bayonets on their rifle.
This is a whole list of the weapons that most of the countries had used as below it's a small documentaries about weapons.