Troll your friends, and kill them with air, LITERATELY.
It is a block of air, so it is invisible, it one hit's anything, and the death message looks like:
Enderkiller08 was killed by BlueBlimpyBanana using "A Choke Hold"
The weapon comes pre-named, so all you have to do is give, place, paste, activate, and KILL
*Still waiting to test*