I had the passing thought of getting revenge, I mean protecting your items from thieves by using a strong contact poison. Now in the case of coins, would a casting of Prestidigitation be enough to make touching them safe again? What about removing all poison from a quiver of arrows? Say you were facing a nasty rogue who had a quiver full of dangerous poisoned arrows that have been making for a tough fight. Or perhaps you're facing a band of drow and their sleep arrows.
The spell can clean things, and possibly depending on the type of poison used, you could easily consider it dirty. So maybe the kind of poison matters?