I foolishly equipped the Giant Zombie with the lightning chaingun, and he made such short work of me next to the respawn point that the game went like this (all in the same method):
1. Respawn the player by creating a new player object with full health. Go to a subfunction, and update the world to make sure he was added properly.
2. Player object is dead inside the update step (in less than a frame)
3. Finish the function by doing some extra work with the freshly spawned player object when refreshing the UI -- uh oh! What happened to the player? Holy shit...
Normally, this wouldn't happen. However, it was happening so fast that I was respawning, dying and encountering this bug all in the same frame (about once every 300 respawns -- and yes, I was dying and respawning that fast). Bizarre.