Dallas M asked on the zombie social network that is G+ "What's your favourite B/X death condition? I usually do 0 = death."
The first thing that sprang to mind -- because there's something wrong with me -- was this:
At 0 Hit Points you explode, doing d6 per level damage to everyone within a radius of feet equal to your Constitution score.
It's more or less the Heart of Woe magic item from Warhammer, but everyone gets it because exploding player-characters are great fun and you shouldn't be stingy with fun.