Back when Planescape first came out, I played with a DM who was a little new to things.
He had us make sixth level PC's, then immediately sent us to "Dwarf Heaven" where we stole some uber-axe from the Dwaven Gods. We were then comanded to use that weapon to murder all the dwarf gods - and we succeeded!
We also used this axe to chop down the central mountain range that housed the dwarf gods.
Things were going "well" until the barbarian weiling the axe fumbled. He drop the axe, and it cut the world in two.
We were of course saved by a friendly group of Mercane, who just happened to be passing by in their Nautiloid Spelljammer.
Mind you, this all happened in the first four hour game session, after making up PC's!
There was no second session.