Mecha

Gunmen 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 Energy(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-Ganzan 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 Gunman are 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.

Gurren Lagann
The Gurren Lagann (グレンラガン, Guren Ragan?), the titular mech of the series, is piloted jointly by two pilots for most of the story, with the Lagann portion always operated by the series' main protagonist Simon and the Gurren piloted by Kamina initially and then various other characters after his death. The mech was originally formed as a hotblooded response from Kamina to the Enki's initial two-headed configuration. Later in the series the land-bound Gurren Lagann merges with another unnamed enemy Gunmen and gains a permanent set of wings. After the Battle of Tepplin, the Gurren Lagann is seen as a symbol of humanity's triumph, and later, after the AntiSpirals, preserved as one of the last true Gunman and the personal machine of Gimmy and Darry.

Lagann
The Lagann (ラガン, Ragan?) is Simon's personal Gunmen which he finds in the first episode while digging tunnels in his village. It received its name, Lagann (羅顔), meaning "enveloping face", from Kamina and draws power from the Core Drill, a small golden drill Simon uses similar to an ignition key. Unlike any other Gunmen in the series, the Lagann sports a unique cockpit and stands just short of an average human adult as opposed to the others which are all mostly the sizes of small buildings or larger. This physical handicap, in tandem with the usually average level of fighting spirit supplied to it by Simon, puts the Lagann at a considerable disadvantage in single combat against enemy Gunmen. However, when Simon is driven to give his best during combat the Lagann's power increases exponentially, giving it the unique ability to generate drills from nearly any part of its frame. Lagann's other and most notable power is the "Lagann Impact", its trademark ability to combine with other machines by piercing them with its drills. It's through this ability that the titular Gurren Lagann is created, along with the other more large-scale mechas in the series.