kryptonite...
Pre-Crisis, there were numerous types. These were:Green Kryptonite: weakens and eventually kills super-powered Kryptonians. Usually harmless to other races, but one story in Brave and the Bold had a device used which resulted in Terrans being affected similar to Kryptonians.
Anti-Kryptonite: similar to Green K, but affects non-super-powered Kryptonians. This was a retcon used to explain why the non-powered Argo City residents could be killed by what seemed to be Green K.
X-Kryptonite: Only one chunk, it was created by Supergirl trying to find a cure for Green K. It gives Terrans, or at least Terran cats, Kryptonian style powers for a limited time.
Red Kryptonite: Causes a specific, odd, effect. Often involved physical transformations or mental changes. Each chunk had a different effect, and could only affect a given Kryptonian once. Effects usually wore off in 24-48 hours. Created when Green K passed through a space cloud.
Gold Kryptonite: Removes a Kryptonian's super-powers permanently. Created when Green K passed through a different space cloud.
White Kryptonite: Kills any plant life from any world. Yep, another space cloud.
Blue Kryptonite: Has the same effect on Bizarro Kryptonians as Green K does on real Kryptonians. Created by the same imperfect duplicator ray that created the Bizarros.
Jewel Kryptonite: Remnents of Krypton's Jewel Mountains, it allows Phantom Zone residents to focus their mental energy and cause explosions in the outside world.
Two notable fake varieties are Silver and Yellow K. Silver was used to keep Superman from closely investigating what turned out to be a 25th (silver) anniversary gift for him from his friends, and Yellow was used by Luthor to fake out what he thought was Superman. It turned out it was a Superman robot ordered to react to Kryptonite like the real thing. When Luthor found this out, he returned all the gold from Fort Knox which he'd stolen.