Tengen Toppa Gurren Lagann

"Even when trapped by karma's cycle...The dreams we left behind will open the door! Even if the universe stands in our way! Our seething blood will determine what will be! We'll break through time and space! And devour all who would stop us, to grab hold of our path! TENGEN TOPPA GURREN LAGANN! JUST WHO THE HELL DO YOU THINK WE ARE?!?!?!"

- Team Dai Gurren

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

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.

History
By combining his own Spiral Power 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 Power (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 Power 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  in the torso, Yoko  in what seems to be either the right shoulder or the right shin, and Leeron  in the left hip. The rest of Team Dai-Gurren are positioned at various points in the limbs and appendages, 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' 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).

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 Power 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 Power, the people observing the battle would, at the very least, have been permanently blinded purely from the amount of visible light released.
 * Tengen Toppa Gurren Lagann is the only form of Gurren Lagann that does not use a Giga Drill Break at any point. Arc-Gurren Lagann uses one against Cathedral Lazengann in movie continuity, Super Galaxy Gurren Lagann uses one against a larger Ashtanga, and Super Tengen Toppa Gurren Lagann uses it against the Anti-Spiral's Super Granzeboma.