It does not have to be "standard" poison or standard radiation.
Alternately, say you rig a gun, bag, etc that are classes of booby traps, the sort of stuff thieves like to steal. So you have a wealthy player who hates thieves keeps a spare "booby trapped" set of grenades in his pack, or a middle of the road person has a booby trapped SMG.
Basically identically looking stuff - the deadliness of the trap based upon the skill of the maker-
Guild crafters could make all kinds of stuff for guildmates that would make thieving a bit risky. As it stands, there is little to no risk to stealing. I might just spend some time standing in the bank, my pockets full of radiated coins, take as much as you like. Now that would be funny.