When Theseus traveled on the road to Athens, he encountered numerous bandits/serial killers who had unique murder methods. Theseus offed them with their own methods. These included:
Epidaurus, who would beat people to death with his club.
Siris, who would tie people between two trees that he had bent down. Then he let go of the trees, ripping them in half.
Sciron, an elderly man who would ask passersby to wash his feet as a sign of respect. When they bent over to comply, he would punt them off a cliff and into the jaws of a sea monster at the bottom.
Cercyon, who would challenge passersby to wrestling matches, then kill them after they had lost.
Procrustes, who would invite passersby to stay the night at his place. If they were too short for the bed, he would stretch their bodies until they fit. If they were too tall for the bed, he would chop off the excess.
The fate of King Diomedes of Thrace, who owned four man-eating mares. One of Hercules's labors was to steal said mares, and Hercules accomplished this by feeding Diomedes to his own animals, which somehow made them tame enough to capture without a fight. (In some versions, Hercules did this in revenge after the mares had eaten his young friend Abderus, even though Diomedes wasn't involved in Abderus's death.)
Heracles' own death was an ironic version of this (and a rare case of it happening to a hero). Soon after marrying his third wife, Deianira, a lecherous centaur named Nessus offered to carry her across a river, but attempted to rape her once they got to the opposite shore; the hero heard her cries for help, and shot the creature with an arrow (envenomed with the blood of the Lernaean Hydra) from the opposite shore, mortally wounding him. As he lay dying, Nessus plotted revenge. He feigned regret for what he had done, and told Deianira to gather his blood, saying it would act as a love potion in case her husband was ever unfaithful to her. Later, when Deianira suspected - falsely, alas - that her husband was trying to woo Iole (the daughter of Eurytus, who Heracles had once earned the right to marry - it didn't work out) she used the supposed love potion, smearing it on his garment. It became clear when he put it on that what Nessus had claimed was a Blatant Lie; the Hydra's blood still tainted his blood, and it nearly burned him alive, causing him horrible pain until he decided to die nobly by leaping on a funeral pyre of oak branches. (Poor Deianira realized her error and tried to warn him, but it was too late, and she hanged herself out of grief. But there was consolation; Heracles was taken to Mount Olympus by Zeus as a final reward for his life of heroism.)
The Greeks obviously loved this trope.
In Norse Mythology, Loki is being chased by the Aesir. He shapeshifts into a fish and hides in a river, but on the bank of the river is the fishing net he invented. The gods use the net to capture him.
In Estonian mythology, the hero Kalevipoeg is killed by his own Talking Sword as revenge for the son of the blacksmith who made it that Kalevipoeg killed in a drunken fight. See Kalevipoeg.