Giant Snake-Tailed Chameleon

It is first summoned during Pain's battle with Jiraiya in Amegakure, swallowing Pain's Animal path and turning invisible via camouflage, to conceal the latter and give it stealth-based advantages. After failing to detect it via a barrier technique, Jiraiya summons Shima and Fukasaku to use Sage Mode. Analysing the situation, Shima is easily able deduce the creature's location and restrain it with her Fighting Tongue Bind technique, before excreting a corrosive liquid along her tongue's length to disable it's camouflage. Fukasaku then slices the creature in half, with the Fighting Tongue Slash.

Pain's Assault
In the anime, the chameleon is summoned again by the second Animal Path during the invasion of Konoha. After causing a rampage along with Pain's other summons, it is de-summoned (along with other animal summons) when Pain decides to concentrate his power solely to the Deva Path for a large-scale Shinra Tensei on Konoha.

Fourth Shinobi World War: Confrontation
During the Fourth Shinobi World War, the chameleon is summoned by Nagato, who has been reincarnated by Kabuto Yakushi. Nagato, being controlled by Kabuto, uses it to hide within it's mouth, while the creature is invisible, and then unleash a massive Shinra Tensei on his surroundings to obliterate a portion of the forest while battling Naruto Uzumaki and Killer B. After Nagato revitalises to his youthful appearance by absorbing B's chakra, he has the chameleon use his snake-tail to hold Naruto while he removes his soul. However, both it and the King of Hell get blinded when Itachi throws several kunai into their eyes, allowing him to save both Naruto and B from Nagato.

Trivia

 * In chapters 374, 550 and 551, the snake was depicted with regular eyes instead of the Rinnegan.