The fastball special is probably the most famous tag-team move in superhero fiction where a super-strong hero literally throws a willing partner toward a target. The maneuver first appeared in the Marvel Comics series Uncanny X-Men #100, when Wolverine (James "Logan" Howlett) had Colossus (Piotr Nikolaievitch Rasputin) hurl him in a battle. It quickly became a favorite tactic of the two heroes. It has also been used by many superheroes, some from companies other than Marvel, since.
When executing the fastball special, Colossus—a large and very strong mutant—takes the much smaller Wolverine into his hands and hurls him forward, like a baseball pitcher would throw a fastball. As Colossus is one of the strongest mortal characters in Marvel Comics, this throw can be superhumanly far, on one occasion even having Wolverine reaching an aircraft in-flight. As a result, Wolverine can reach the target of an attack he may not be able to reach otherwise and do it much faster than he would if he ran there by himself. Furthermore, Wolverine's metal-laced skeleton and his healing factor means that he is typically not in major danger of being severely injured in the move.
The fastball special was also reversed once, when Wolverine took advantage of the moon's reduced gravity to throw Colossus at Phoenix. 
The fastball move was revisited in a scene from the comic book series Astonishing X-Men written by Joss Whedon and drawn by John Cassaday. In the story, Colossus, who was believed to be deceased at the time, had just been discovered and released from imprisonment, and one of those responsible was escaping in an aircraft. Wolverine asked Colossus if he was capable of physical effort after his long imprisonment, and when Colossus replied that he was, Wolverine said, "I have two words for you." The next frame, a full two-page spread, showed Wolverine in mid-air and Colossus far below in a "follow-through" position, obviously having just launched his teammate; no dialogue was used in this frame, the picture speaking for itself to readers familiar with the maneuver.
In the great majority of the cases, Colossus hurls Wolverine. However, there has been also one case in Uncanny X-Men #137 (last part of the Dark Phoenix Saga) where the X-Men were on the Moon and Wolverine threw Colossus, making use of the moon's weaker gravity. Other variations include Colossus being thrown by Rogue and Colossus throwing Shadowcat.
Another scene involving Wolverine throwing Colossus occurred in an issue of Wolverine, in which Wolverine is (temporarily) killed and meets up with Colossus in the afterlife, where the duo are attacked by slain villains. Wolverine then promptly picks Colossus up; the confused Colossus asks, "Didn't this used to go the other way around?", to which Wolverine replies "Haven't you learned to improvise since you died?" before hurling Colossus at the angry mob.
Another notable fastball special featured Shadowcat and Spider-Man in a Marvel Team-Up special, where Kitty's phased molecules made her fly weightlessly through the air, whereupon she solidified herself and landed with full impact against her target, a rogue Morlock who was attacking surface-dwelling humans.
During the first fight of the X-Men after Operation: Zero Tolerance which included the new members Cecilia Reyes, Maggott and Marrow, a fastball special was performed by Marrow and Maggott, with Maggott throwing Marrow against an enemy in the same manner as Wolverine and Colossus.
When Nightcrawler, Colossus and Shadowcat returned to the X-Men after the disbanding of Excalibur, Rogue performed what she would later call the Deathstar Drop, as an homage to the fastball special. It basically involved a flying Rogue throwing Nightcrawler.
In Marvel Team-Up (vol. 3) #6, Spider-Man throws X-23 into Titannus. Spider-Man jokingly wonders whether the X-Men have trademarked the fastball special, to which X-23 responds that it will be "our little secret".
The move was recently spoofed in the Great Lakes Avengers Christmas Special as the Fuzzball Special, in which Squirrel Girl hurled her current squirrel companion, 'Tippy Toe', at MODOK, causing him to cry 'Not in the face!'. They also have a defensive version of the Fastball Special, shown in Deadpool #10, where Flatman throws Doorman over a hostage (actually, over Blind Al), in theory to teleport the target into safety.
The move has yet to be carried out in Ultimate X-Men aside from cover art, although Colossus mentions having thought up the move in the Return of the King arc. However, in Ultimate Spider-Man, the X-Men made a special appearance alongside Spider-Man, Shadowcat's boyfriend, when both parties were kidnapped by Deadpool and the Reavers (Ultimate). During the battle, Colossus threw Shadowcat at one of their antagonizers, completing the move. She stayed intangible the whole way, phasing through the cyborg and thereby shorting it out.
In other media
In the X-Men Legends series of games, any character with the Might skill—Rogue, Beast, Juggernaut and Colossus—or a Might skill used in a special form—Emma Frost and Magma—can perform the Fastball Special by pushing the Throw button next to Wolverine.
This maneuver was carried over to the series' spin-off Marvel: Ultimate Alliance, where the Fastball Special can be performed by the Thing, Colossus, the Hulk, Luke Cage or Captain America. Also, aside from Wolverine, Mr. Fantastic can be thrown too, but only when using his "Pinball" ability (in which Reed curls himself up into a ball).
In the first X-Men, there is a variant of the move where Jean Grey and Storm cooperate using their powers to throw Wolverine to Magneto's machine in the torch hand of the Statue of Liberty.
In the film X-Men: The Last Stand the move is used twice - when Colossus hurls Wolverine at a Sentinel in a Danger Room sequence and, later, at Magneto. In this incarnation, the fastball special is executed rather like a hammer throw, with Colossus whirling Wolverine around first like a hammer before releasing him.
In one episode of the animated series, when the X-Men are attacked by a group of mutants on the back of pterodactyl-like creatures, Wolverine says to Beast "Fix me up a Fastball Special!", whereupon the latter throws him up in the air to take out one of the riders.
Actually, the Power Puff Girls did this once, even mentioning it by name, in the episode Film Flam.