Talking about ars moriendae, just after 3.5 came out, I emailed my group with some of the changes to the rules. In particular, I mentioned that harm could now kill on a failed save.
One of the players replied, full of bravado, saying things like "it's about time, adds spice to life", etc.
The next session, he charged an evil bloodmage, and copped a harm for his trouble. I asked whether he wanted to use a hero point to boost his save. He said "nah, I'll be fine".
Then he remembered it was a Will save, not a Fort save. So he failed his save, and died.
The group drove off the bloodmage, trudged back to town, and got him raised.
The session after that, they were exploring the dungeon underneath where they fought the bloodmage. After some time, they met a lich.
The same guy charged the lich, and copped another harm for his trouble. And again, he failed his save and died.
It's become a bit of a running joke in our group ever since....