Rattler (Gustav Krueger) is a supervillain appearing in American comic books published by Marvel Comics. He first appeared in Captain America #310 (October 1985), created by writer Mark Gruenwald and artist Paul Neary. The name Rattler was also used by two Marvel comics characters from the Wild West era, both enemies of the Rawhide Kid. A fourth Rattler appeared in the Spider-Man newspaper comic strip, who gained superpowers after being bitten by a snake and treated with experimental anti-venom.

Krueger, as Rattler, was given a long bionic tail that emits sonic shockwaves to mimic his reptile namesake. He first appeared as part of the Serpent Society, a team of snake-themed villains for hire. During their first mission, they were opposed by Captain America, who would have several run-ins with the Society. Rattler was one of the Society members who sided with Viper when she took over the group, but remained with the group after she was deposed. At one point he was part of the Thunderbolts, but returned to the Serpent Society. He remained a member when the Society was reorganized into Serpent Solutions.

Rattler first appeared in Captain America #310 (October 1985), created by writer Mark Gruenwald and artist Paul Neary.

Rattler is originally from Germany and wields a bionic tail which he uses to create shockwaves and vibrations. During his initiation into the Serpent Society, Rattler is ambushed by Captain America, but uses his tail to protect himself and stop Captain America's shield from doing any damage. He later battles Captain America again after being tricked by the Porcupine, along with Diamondback, Death Adder, and Cottonmouth. During the ensuing fight with Captain America, Rattler uses his tail to send vibrations coursing through the hero's body, disorienting him. However, he is eventually thrown into a pillar by his tail, knocking him out. Alongside Cottonmouth, Rattler confronts Kingpin's men after Death Adder is murdered by the Scourge of the Underworld.

Rattler participates in the Serpent Society's mission to recover mystic objects for Ghaur and Llyra. After learning that X-Men member Longshot had found the missing artifact on his own, Rattler creates an avalanche by rattling his tail, taking himself and Longshot out.

Rattler remains a member of the Serpent Society under Cobra's leadership. After the group had captured and chained Captain America and Diamondback (really a Life Model Decoy) in this underground New York headquarters the pair escaped. S.H.I.E.L.D. subsequently took Rattler and the rest of the Society into custody.

Rattler joined the group of criminals aiding the Thunderbolts during "Civil War", alongside fellow Serpent Society members Cobra and Bushmaster.

In All-New, All-Different Marvel, Rattler appears as a member of Viper's Serpent Society under its new name of Serpent Solutions.