Ye Olde Poisonous Poison is massively helpful in killing Mary Sues. The PPC generally likes it because it is a fanwritten creation; if reality-type stuff is more to your taste, try curare. Ye Olde Poisonous Poison's biggest moment of fame was in the first death of Maeluiwen in "The Most Interesting Adventures of Maeluiwen," when Gríma shot her with a poisoned dart for sleeping with Éowyn. Since its introduction, it has become a very popular way of disposing of unwanted characters, and, occasionally, fanwriters.