Rifle: The rifle has been the main weapon of all infantry men, and originally fired a lead ball, and was extremely inaccurate. But during the 19th century, rifles began to be made with smaller bores, and could now fire multiple shots a minute. This newly created rifle had an accuracy of over 600 meters, but could actually fire from up to 1,400 meters but wouldn't hit what the shooter was aiming for. Each country had it own version of the rifle, like the German Mauser, or the French Lebel. Finally, every rifle always had a bayonet attached to it, or an area where the shooter could attach one.
Mortars: Mortars became useful dealing with enemy trenches, and people began to favor short ranged mortars instead of the large long range mortars. Mortars fired grenades and other explosives, and normally needed 1-2 men to operate. When a mortar was fired it could easily be heard and sent troops searching for cover.
Machine Gun: This large weapons took a team of 4-6 people to operate, and could obliterate multiple enemy troops in a matter of seconds. The machine gun was capable of firing multiple rounds in seconds, and were commonly grouped together to hold a defensive position. This kind of weapon was cooled either by water, or cooled by air. Even with these cooling methods, Machine guns would still heat up quickly, usually in about two minutes especially in hot conditions.