Okay, I'll give it to you -
Napalm Death hold the record for the shortest 7" single, You Suffer, released (I believe) in 1988 as part of the John Peel sessions... they are labelmates on Earache records with Brutal Truth, who hold the world record for shortest promo video, but I don't know what the song was.
Since I gotcha, here's another question -
What other Earache band is currently having their latest album ratified by the Guinness officials to qualify for entry as the fastest human drumming on record? Here's a hint - the song being ratified is a Carcass cover.