The first campaign I ever ran is still to this day my very favorite. I had played in several games beforehand, so I knew the system pretty well.

Anyway, it started out fairly standard, the PCs were running errands for their main contact who had hired them at the beginning. The tasks they were doing kept getting progressively worse, until they realized that he was evil and they were unwittingly aiding in his evil schemes.

So they confront the guy, just as I had planned. He was an epic level mostly-cleric multiclass who killed the whole party in just a few rounds. The players were all like WTF!?

Then I pulled out a book with undead templates and info and said "So you're all ghosts now..."

They loved it.