One of the coolest magical weapon in every edition is the vorpal sword. Player dreams about finding in a treasure stash late at night, as they lie on their beds looking out at the stars. It might find its way into their doodles. VS + DG 4E.
Or maybe that’s just me.

The vorpal sword comes from the Lewis Carroll nonsense poem Jabberwocky (opposed to all of Carroll’s non-nonsense and utterly serious poems). The line in question is:

One, two! One, two! And through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.

From that was born a legend. While the effectiveness of the sword is vague in the source material, and its decapitation abilities are extrapolated from the lines about carrying its head back, this is all largely irrelevant now. The sword’s potency has passed into the collective subconscious, as seen by its appearance in the Tim Burton reimagining of Alice in Wonderland and in the comic book Fables.