As written in the Monster Manual, there are only two ways to actually kill / destroy a vampire:
1. Prevent it from returning to its place of rest within 2 hours of dropping it to 0 hp
2. Drop it to 0 hp while it is in sunlight or standing in running water.
That's it. Stake through the heart while in its coffin? Just paralysis. Chop off its head while in the coffin with steak through the heart? Nope, unless that critical wound happens to do 144 damage with a single blow. Heck, even staking it and submurging it in holy water will simply have it paralyzed and unable to regenerate, but it still won't be destroyed.
Seems a bit much, eh?
I ruled that chopping off the head while staked in the coffin did the trick, as that is pretty common in movie lore. Thoughts?
I'm surprised you can't do it with a wish.
A Wish could prevent it returning to it's place of rest or ensure sunlight became part of the equation... 
Besides - once you've got the sucker staked it's yours to toy with unless you've got other problems to deal with.
I like vampires to have very limited ways of being destroyed... it adds to their ability to be the recurring villain, which I like for them to be, even if only for the first vampire or two that the party encounters - once they figure out how to kill them for good, throwing more vampires at them is fun so they can get that "we're totally awesome" feeling when they jab a few dozen vampires in the heart with stakes and leave them for the sun (since the stake paralyzes and the sunlight causes 20 radiant damage every turn and shuts off their regeneration).
Nothing wrong with adding ways from lore to destroy vampires. I require the chopping off the head to be followed by filling the head with holy wafers and burning it myself.
AaronOfBarbaria wrote:
Bumamgar wrote:
There are a few more methods i would accept like concecrating its place of rest and blessing the body after anointing it with holy water, technicaly this leaves the vampire trapped outside its body forever unable to interact on the physical plane, but it can become quite a nasty hazard on the astral plane.
I don't have the MM yet, but the Basic DMG has Vampires. Is there a sidebar on the Vampire entry that talks about variants or "unofficial methods"? Like, in the "how to kill a vampire" section, does it end with something like "These are the confirmed ways to kill a vampire. Others may exist." I remember both 3.x and 4E saying things like that in their entry.
Also, is there a "wolf polymorph" variant? Dracula (and allegedly that Ravenloft guy) were big on turning into wolves, not just bats. I might just have to make a variant power for other creatures of the night ^_^