This story comes from one of our earlier adventures in my friend's realm using Dungeons and Dragons, Second Edition rules. In this adventure, I was playing a ninja at about third level. The two other players were playing a paladin and dwarven fighter, both at about second level. I don't recall most of the events that led up to this moment, but the important detail is that we had met this high-level knight in a very old castle in poor condition. While he didn't seem interested in helping us or even spending any time talking to us, he was clearly not an enemy. Seeing no reason in spending any further time there, we left, not really knowing what to do next.
It wasn't long before we reached a bridge and encountered a death knight with skeleton minions. Clearly, second and third level characters with almost nothing in the way of magical equipment were no match for a death knight, so naturally we were very concerned. The knight, however, showed up to save us; he had a great deal of powerful magical equipment and thus actually had a chance for survival. He demanded that we go on while he was distracting the enemy, and certainly, it was the only sane thing to do. In fact, that's what we did.
But that was as long as my sanity lasted. As we were riding away from the scene, I was bothered by the fact that we had just left the knight to face one of the most dangerous of undead creatures by himself, even if he was far better equipped to deal with a death knight. I knew that turning around and trying to help would likely be suicide, though, but I felt as though honor was at stake.
So, even though it was completely crazy, I managed to convince the other two to turn around and head back. I was somewhat surprised they agreed to it, being as this was an entirely stupid decision. I had every reason to believe that we were sending these characters to an early grave.
But my friend, the dungeon master, decided to be kind. Since he believed I made the decision from playing my character's honorable streak, he decided to spare us this time. The death knight was amused by our foolish decision to return, and thus he satisfied himself by using his word kill on the paladin's horse. The poor paladin was thrown and took damage when the horse rolled over her, but that was the extent of the damage we took from the death knight. The skeletons that were left behind were no match for us, especially with the knight helping us. He had a mace that was just disintegrating the skeletons, and while it was taking us a little longer to take them out, they were still falling before us.
And thus, my character survived what was probably the stupidest decision I've ever made for any character in any of my games.