CROSS
The last part of your basic triology of vampire Slaying weapons.
The cross is a religious icon that has been credited over the centuries
with being able to defeat all manner of demons. Vampire mansions in old
horror movies always had furniture/candle sticks etc that could be made
into religious symbols.
How To Use
Point it at a vampire and they will back off in fear and anger.
It burns the skin of vampires, so they can not touch it. (see the episode when Buffy hugs Angel and it leaves a cross-shaped burn mark on his bare (down girls!) chest.
Apparently it can work as a stake, even if it is metal. However, studies seem to indicate that a cross will only work on Vampires who were/believed in the Christian faith - Vamp Willow - being Jewish - wasn't affected by Welsey's Cross (see Doppelgangland)
Other uses for a Cross