Tengen Toppa Gurren Lagann

Tengen Toppa Gurren Lagann (天元突破グレンラガン) is the titular mecha of the anime. Design based on the smaller Gurren Lagann, it is the strongest mecha in the anime, but the movies give that title to Super Tengen Toppa Gurren Lagann.

History
By combining his own Spiral Energy with his comrades, Simon created the true titular entity, which he titles, Tengen Toppa Gurren Lagann, in the final battle against the Anti-Spirals. Not actually a mecha by traditional means, the Tengen Toppa Gurren Lagann is actually a mass of continuously materialized Spiral Energy (similar to the Spiral technique used to materialize Drills) on the scale of a galaxy.

Though being similar to the Gurren Lagann, its design is overall very different from other mecha in the series, its armor being made up of red skulls, illuminated by the storm of Spiral Energy that burns continuously from its core, giving it the appearance of Team Dai-Gurren's emblem. Of its many faces, the primary "cockpits" contain: Simon and Nia in the head, Viral  the torso, Yoko  in the right shin, and Leeron  in what seems to be the left forearm. The rest of Team Dai-Gurren are positioned at various points in the limbs and appendeges, all operating in Lagann-style cockpits. Its abdominal jaw is clenched onto the head of the Lazengann, containing a fully resurrected Lordgenome.

It has been confirmed in the data books that the Tengen Toppa Gurren Lagann is 10 million light years in height, making it roughly one hundred times the size of the Milky Way Galaxy. It is the the third largest mecha in anime to date, the other two being the Super Tengen Toppa Gurren Lagann, and the Super Granzeboma.

Tengen Toppa Gurren Lagann draws jointly on abilities from its many pilots, including Simon's drills, Yoko's rifle, Viral's swords and so on. The actual limit of the mecha's abilities is immeasurable, as it gains an infinite amount of power depending on the pilots' will to win. At points, Tengen Toppa Gurren Lagann and the Anti-Spirals' Granzeboma fight at forces equal to the Big Bang, the battle being so intense it was shown to rip holes through various dimensions showing that the power of each was on a extreme scale. This is furthered by the fact that they can alter the fundamental laws of reality, such as altering probability and creating matter out of thin air (which is no small feat even by the series' own standard, as the various drills and weapons materialized are larger than most small galaxies).

Appearance
Tengen Toppa Gurren Lagann resembles the original Gurren-Lagann, albeit with a more intensely themed appearance. Its armor is covered in various draconic skulls and faces; since the number of total faces is equal to the number of key pilots of the mech, it can be assumed that these are its cockpits. The head wears a more symmetrical version of Lagann's helmet, while the chest face wears a pair of non-functional sunglasses. Its abdominal mouth is clamped onto the Lazengann's head, which Lordgenome can detach and use to create a galactic-scale Lazengann.

Tengen Toppa Gurren Lagann, bears striking resemblance to Super Robot Wars/Taisen Original Generation's Persönlichkeit. It is quite possible that Tengen Toppa Gurren Lagann is based of Persönlichkeit, due to the reason that Gainax also participated in many productions of Super Robot Wars/Taisen.

Trivia

 * Theoretically if the Tengen Toppa Gurren Lagann is 10 million light years across, it would mean that its eventual battle with the equally large Granzeboma would last several billion years, considering that nothing can exceed the speed of light. This would mean that swinging an arm alone might be a feat that would traverse several million light years, which will require the same number of years in real time, to execute. However, since relativistic physics are taken into consideration, it would mean that the Tengen Toppa Gurren Lagann experiences severe time dilation effects that would theoretically make what seems to be a billion years last only several seconds, if the battle occurs at near light speed. Thus, the battle shown might be a condensed event that occurs not from the observer's objective time frame, but from the Tengen Toppa Gurren Lagann's subjective time frame. If the battle really took several billion years though, in actuality, the galaxies should dwindle in terms of their stellar intensity due to the end of solar rebirth cycles caused by the heat death of the universe, assuming a situation whereby a big crunch does not happen.
 * Another possibility is that the "movements" of the mech are actually the mech teleporting its body parts around to block and attack. Instantaneous teleportation is possible according to the storyline and it would seem as if the robot was actually making fliud motions. It would allow the parts of the mech to move millions of light years at a time, making it entirely possible for a battle of that scale to occur. We must assume that since the Granzeboma was made to counter the Tengen Toppa Gurren Lagann, it would operate using basically the same principles.
 * Most likely, however, is that Tengen Toppa is simply capable of moving faster than light even if the torque of its joint movements do not hint as such. This fits right into the theme of Simon's speech prior to the initial formation of Tengen Toppa - Team Dai-Gurren doesn't care about the impossible.
 * It is possible that the final battle between Granezamboa and Tengen Toppa Gurren Lagann happened in a completely separate dimension. As stated by LordGenome, "A Super Spiral Universe, where thought is given form." This could be an explanation as to the speed of the mechas, as well as why the people on Earth were able to watch it unfold as the viewer could though the portal. It also dismisses any worries of genocide in the cross-fire, since the galaxies are mostly empty of life.
 * The second movie implies that the Tengen Toppa Gurren Lagann is an organic, living being; as the Anti-Spiral rips it to pieces, flesh and blood can be seen in gratuitous amounts.
 * If Spiral Energy did not defy the law of conservation of energy, Tengen Toppa Gurren Lagann would have been so massive that entire galaxies would have been pulled towards (and possibly merge with) it due to gravitational attraction.
 * Unless the battle between Tengen Toppa Gurren Lagann and Granzeboma involved only Spiral Energy, the people observing the battle would, at the very least, have been permanently blinded purely from the amount of visible light released.