Gunmen or also known as Ganmen are the main type of mecha used in the anime series Tengen Toppa Gurren Lagann. The name itself means "face/facade"(顔面 ガンメン Face Surface), and can be broken down into "gun" and "man" — unsurprisingly, the mecha themselves are centered around faces and as such are very varied with few in the series being the same model. Gunmen sport a variety of weaponry: primitive models only use large clubs or bare hands, while advanced ones use solid or beam weaponry. Gunmen are powered by their human pilots' Spiral Power (fighting spirit), or by electricity when piloted by a Beastman.
The original purpose of the Gunmen was to battle the Anti-Spirals, the main antagonistic force of the series. Lordgenome developed them about 1,000 years before the events in the series on a very large scale, with enormous Gunmen(called Dai-Guns) like the Dai-Gunzan and Arc-Gurren being much more commonplace than the smaller models seen through most of the series. Gunmen were also designed for space combat, so no further modifications were necessary when Team Dai-Gurren was launched with their Gunmen into the Earth's satellite orbit to fight the Anti-Spirals.
After the events of the series, there are very few Gunmen left in existence aside from Gurren Lagann and the Super Galaxy Dai-Gurren, with the large bulk of Earth's military being made up of Grapearls.