DV8: DV8 once contended with a mercenary calling himself Dirge. When Dirge first met Frostbite, he bragged that he once shot nine teeth out of a man's head in nine different shots without hurting him otherwise. The tenth shot killed him, but it wasn't Dirge's fault the guy couldn't keep still.
The Flash: In the two-part Elseworlds story Super 7, Wally West's legs were nearly destroyed in a riot. His contribution to battles is now as a gunslinger, since he has all the time in the world to aim every shot. (For some inexplicable reason he's shown using ordinary handguns. He could probably aim every shot with a machinegun on full-auto.)
Great Ten: Celestial Archer is capable of freaking ridiculous feats with this. He can shoot out the sun and hit a target on the other side of the world. In his defense, his bow is a weapon of the gods and thus is inherently capable of doing that kind of thing.
The self-trained superhero archer Green Arrow, and his families of characters, can ricochet arrows off walls and into targets. And that's not even getting into "boxing glove arrows", "bomb arrows", "net arrows" or "cat arrows" (don't ask). They have, at times, been depicted as so implausibly good, some people theorize that they actually have psychokinesis and are simply using it to show off by making it look like they're the world's greatest archers. The fact that the artists and writers of their titles usually don't do very much research into how archers actually even hold their bows drives it home for a lot of people.
In Batman: The Dark Knight Returns, Green Arrow has lost an arm and still manages to be a crackshot. Green Arrow once lost both arms (he got better) and still managed to pull off a shot by bracing the bow with his feet and pulling the arrow back with his teeth.
Roy Harper, aka Speedy aka Arsenal aka Red Arrow aka Arsenal again, boasts that he never misses — boasts that he can back up. During the Rise of Arsenal storyline, Roy, in a fit of rage, stricken with grief, addled with drugs, and handicapped by his unfamiliar cybernetic arm, breaks his bow, throws it at a bullseye — and hits it dead center. Even when doped up, handicapped, and mentally unbalanced, he never misses. Note that right before this he had missed every actual shot he took with the bow. The point at the time was to recast Roy back into his non-archer gun/knife nut phase. Or to show that he was so messed up he was overthinking his shots.
Green Lantern: Bedovian, a Yellow Lantern and John Stewart, a Green Lantern. The two of them are capable of sniping each other from three space sectors away. Just to give you an idea of how big a sector is, the entire universe is divided into 3600 sectors by the Green Lantern Corps. A conservative estimate would put the size of a sector in the several hundreds of thousands of lightyears.
Stewart and Bedovian weren't necessarily hundreds of thousands of light years away from each other in that instance. The space sectors into which the universe is divided are wedges, with each wedge narrowing as one approaches Oa, the center of the universe. Thus, the closer one gets to Oa, the less distance one has to travel to cross any three sectors. At the time of the sniping incident, Stewart was on or very close to Oa and, if Bedovian was also fairly close to Oa, they may have been shooting across three sectors without being all that far from each other (while not quite as incredible, the distance would still be pretty impressive).
Justice League of America: In his first appearance in the pages of JLA (1997), the villain Prometheus fired a bullet at Catwoman from one of his gauntlet-guns. The Huntress shot the bullet out of midair with a crossbow bolt. This is a woman who, when introduced, was just a schoolteacher who worked out a lot.
Robin (1993): Tim Drake manages to cork the gun barrel of Dorrance's right hand man by throwing a screw into it from a couple of floors up which caused the gun to backfire somehow.
Suicide Squad: The gun-wielding assassin Deadshot has a long-standing reputation for never missing his shot (unless he happens to be aiming at Batman). In a Suicide Squad miniseries, he took out six targets scattered around a room while blindfolded. Not only this, but he has ricocheted his bullets off poles, while turned around, and hit each target with perfect accuracy.
Earlier in the same series, he failed to shoot a target in the bullseye while blindfolded...because Captain Boomerang Jr. had hit all his bullets in mid-air, using bent paperclips. (Admittedly using Super-Speed, but still.). In Outsiders (2003), while in a prison riot, Captain Boomerang Jr. had grabbed and thrown something, bouncing it off the walls, to hit and knock out a fellow prisoner.
One of the only times Deadshot did miss, it was in his youth, a tree branch he was standing on snapped under him, and what should have been a disarming shot became a kill shot. The person he unintentionally killed was his beloved older brother.
In one comic, Superman pretends to be a villain named the Golden Dart, kidnaps Lois Lane, and throws darts at her. His aiming skills allow him to keep himself from hitting Lois, instead missing her by "scant inches".
Thanks to her telescopic vision, Supergirl has literal super-aim. In Action Comics #258 she hits her target from space.
Steve Trevor is a crack shot with his service weapon, and has been shooting chains off of imprisoned allies and similar feats since the early days of Wonder Woman (1942).
Young Justice: Arrowette once shown having a conversation with her mother (the first Arrowette) while playing darts. The camera pans back to show a line of darts driven into each other point to tail, Robin Hood style, from the first, dead center on the target. The ladies decide they really need to find a different game to compete with.
