We all know that some monsters have a Save or Die mechanic based on their mythical lore, but players should also have the reverse abilities. The GM should be willing to let a well prepared character (Not exactly a metagaming player) have all their hard work from preparation show off during the big showdown. Here are just a handful of instant death or at least subduing monsters. If I missed your favorite, or you think I am a thousand miles off base, feel free to leave a comment and start a conversation. 

Called Shot Monsters

Vampire: Called shot to the heart with a sharp wooden object and the fanged atrocity is dust. There are some factors that could draw the combat out a bit. Vampires are basically a blood drinking Super Soldier, every natural talent is boosted making them stronger and faster. 

Creatures of the Night: Almost any night based monster becomes weaker, or flat out dies with sunlight. A mage with a sunlight spell shouldn't have to worry about spell resistance or any game mechanic. If you can produce a miniature sun, it should have all of its effects. Role play not Roll play.

Golems: These walking mindless guardians spring from Hebrew lore, but to stop one you have to be able to get close to the face without being torn asunder. The power that holds them together is inscribed in their forehead, the Hebrew word for life, all you have to do is scratch out the right letter and it becomes death. Taking a few points in linguistics could save your backside in a pinch.

Basilisk: This guy has his deadly breath and gaze, but you can fight fire with fowl if you know where you are heading. In the lore of the Basilisk, it could be killed simply by hearing the call of a crow or chicken. Here's the rub though, the description of the Basilisk puts it at being an Egyptian Spitting Cobra... They don't have ears and thus cannot hear. Sorry you are on your own there.

Different Ways To Stop a Charging Foe

Werewolf: This one is a bit tricky, and requires lots of gathering information. If you know the name of the werewolf you can throw a chunk of metal over their head and call their name. This reverts them back to their rational self, and later became the Silver Bullet myth.

Mummies: Seriously, bring a house cat. Egyptians worshipped cats as guardians of the underworld. Believing that animals intense attention to nothing was an alert that something was not right. That scene in The Mummy where Brendan Frasier holds up the cat, yeah that really works, or at least should.