This isn't entirely the DM's fault, but...

.. we were underground, our party of ~ 4th - 5th level characters, with the knowledge that there were trolls around waiting to kick our asses. I should point out that this was AD&D I suppose. Anyway, the six of us decide to hole outselves against a dead end, and use this magical rock we found which, when the command word is uttered, grows into a sort of home, with beds and everything. Some of the characters elict to sleep inside the home, the others decide to stay outside.

The DM asks us 'how many hours are you sleeping in it?' the reply is naturally '8' so we're fully rested.

DM: Ok. You're all dead.

Needless to say we were shocked a bit. He explained the house only would stay open like that for 8 hours, thus crushing us if we were still inside. Bam. Campaign over.

Now, the funny part (if you can call it that) is that it was discovered that the portable home thing only works once a day... and that was our second attempt at using it. No takebacks however on that day.

- Eddie