Soak slices in poison then serve it in a salad.
Bash them so hard in the throat with it that their esauphogus collapses.
Cut cuke in half. Shove the cut end of one half into the mouth of a corpse, and the cut end of the other half in the ass of the same corpse. Let intended victim see this corpse, and tell them they have eaten one of the same kind of seed this guy had. They will have an anxiety overload and possibly a heart attack.