It's said that Mustard Gas was used for the first time.
Grenades,Mines and Submarines as well.
There was also Tanks, but because of all the mud, they would sink quickly.
Mostly heavy artillery, and rifles; and later, poison gas, mustard gas; burn your lungs out.
Battleships (called Dreadnaughts based upon the design of HMS Dreadnaught), Battlecruisers, cruisers, destroyers, submarines, and one aircraft carrier.
Pikes, Catapults, Swords, and Shields
Machine Guns and Tanks. Tanks were actually introduced during the Battle of the Somme.
guns guns guns yummy buns