So I have this adventure I wrote for Con games called "Up From Darkness" (available from RPGNow if you want to give it a look) that I have run now for two years and its my favorite thus far to run as a one shot.
True to the name of the adventure, the PCs wake up in darkness, buried at the bottom of a dungeon, with no memories (as a one shot, the amnesia factor is easy to pull off), and no equipment other than white silk kimonos, and they must climb their way up from the darkness. As they do so, they slowly regain memories discovering why they were there and who they are. While that sounds pretty basic, the manner in which it plays out is delicious.
In both games I ran of it this year at Origins, I had five deaths in each game. In one game there was a PC suicide, a PC who was ritually sacrificed by the others, one death by massive falling rock, and two PCs killed by monsters. And, though there were only five players, and five PC deaths, two of the PCs made it through without dying at all (which, in the context of the adventure makes sense). In the other game this year, there was a PC who bled to death at the bottom of a spiked pit trap (the spikes were barbed causing bleed damage), a death by spear trap, a death by falling, a death by fireball trap, and one monster kill. In that adventure, in the sacrifice room, one of the PCs was begging the other PCs to sacrifice him, but the action was prevented by another PC who found the idea rather disturbing.
The adventures internal ability to allow the GM to go after the PCs hard is very fun and the dungeon is full of lethal traps. The last monster has a poison which, when the save is failed, strikes the character blind and more than one PC has left the dungeon permanently blind, with a minimum of hit-points and felt good about having done that well.
The best thing about the adventure, however, is not the lethality but the subtle nature of the memories that slowly come to the PCs (using a mechanic that they gain a small memory [prescripted] when they achieve a certain goal or whenever they roll a natural 1 or 20; and a large memory at preset points in the dungeon). Quotes like, "I am beginning to remember things, and I don't think I am a very good person," or "I am starting to wonder whether or not we are actually dead and in some sort of hell," are typical with the adventure. And when the last reveal is made and the players realize who they are and why they were in the dungeons, there have been a plethora of good quotes at various games. One of my favorites is my wife (who playtested), saying, "That was very disturbing." My son ran the game at Origins this year, and one of the players came over to my table afterwards to shake my hand, saying, "Well Done." When you can write an adventure in which you regularly, over the course of 4 hours, kill, mutilate, blind, cripple, burn, and otherwise hurt the PCs (eight PC deaths is my current record with the adventure), there are PC suicides and PCs begging other PCs to sacrifice them on a black altar, and they still at the end, thank you for the experience, I have to think you have done well. I'm kinda proud of this one.