Arm-Fall-Off Boy has the ability to detach his own limbs, which he can then use as blunt weapons. He can literally tear off his arm and beat you with the wet end. He first appears while trying-out to join the Legion of Super Heroes. Unsurprisingly, his attempt fails.
Much later, he made another attempt, now using the name Splitter. Unfortunately the pressure was too much for him and he literally fell apart.
It’s not certain how the self-amputating hero, real name Floyd Belkin, got his unique powers. It may have been because he mishandled a dangerous element, although in recent continuity it is suggested his arm first fell off shortly
after birth; a nightmare, of course, for any new parent.