Your aim was off, so you did not hit me. I then shoot you with a nuclear laser before extracting the radioactive material from the knife.
I trap the next user in an indestructable tank filled with sodium hydroxide, which begins dissolving away their flesh.
Wud da fug?
You used potassium ferrocyanide, which is a non-toxic cyanide compound, so nothing happened.
I poisoned the next user with both hydrogen cyanide and potassium cyanide in equal amounts of one gram.