Maxim machine gun
The Maxim machine gun was the world's first practical fully automatic single barrel machine gun. It was invented by Hiram Maxim in 1883, and was adopted by virtually every combatant nation in World War One and called by many different names.
It first saw significant action in the Russo-Japanese War, where both sides bought vast numbers of Maxim's guns. Nearly 50 per cent of all casualties in the entire conflict were derived from Maxim guns. On the Western Front of WW1, 90 per cent of bullet related casualties were inflicted by Maxim-type guns, including the Vickers which was an improved and redesigned Maxim introduced into the British Army on 26 November, 1912 .
Compared to modern machine guns, the Maxim was extremely bulky and awkward, typically requiring a four to six man team to operate it. However, at the time it was the only alternative to slow firing bolt action rifles, and its extreme lethality was employed to devastating effect against obsolete charging tactics. It fired .303 bullets at 500 rounds per minute, effectively giving it the firepower of 100 rifles.
A later, lighter model of the five man Maxim was ominously nicknamed the "Devil's Paintbrush" in reference to the sight of whole rows of charging soldiers being cut down in a line. It was reputedly the single most devastating weapon ever used, causing even more casualties than the atomic bomb.