ROFL! I DM'd "The Sunless Citadel" early this morning, and I have already killed a PC!
The PCs were at the final battle, and for some unknown reason, the Paladin on the party went on a mad rush and charged into the center of the enemies. What the PC didn't know was, in addition to the regular baddies, this final battle was joined by a group of sub-villains that were driven away earlier in the adventure.
So, the fight turned out to be harder than it should have been. The Paladin was summarily surrounded, had
heat metal cast upon her, and then butchered by the hobgoblin chief. After she dropped, the
heat metal spell finished her off.
I have never seen such shoddy planning before. The funny thing is that the other PC is an expert real-life strategist, but the player of the Paladin refused to listen and just charged ahead. I laughed.
Now, had the PCs followed the strategist's advice, they would have advanced 10' at a time, used ranged weapons, and kept close ranks, forcing the monsters to advance or retaliate with their own ranged weapons. Combine this with the fact that the strategist was playing a Gestalt Drow Sorcerer/Favored Soul of Eilistraee, and a win would have been a sure thing; the character had a silly amount of spells at her disposal, including
sleep.