- Dying on your first turn.
- Death by falling off of horses.
- Dying by kicking something.
- In SLASH'EM, death by fishhook to the face. Or by hitting yourself with a grappling hook in NetHack.
- Typically, a potion of gain level grants you an instant level up. A cursed potion of gain level warps you to the floor above. That is, you gain a dungeon level.
- Any YASD can give a Space Quest game a run for its money.
- Hallucinating and seeing what any of the other monsters will turn into.
- If you throw a cockatrice corpse up (be sure to wear gloves!) while not wearing a helmet, it will fall on your head and turn you to stone. The game states the cause of death as "petrified by elementary physics."
- Heck, any time the cause of death reaches Deadpan Snarker levels.
- "The kitten eats a little dog corpse."
- The fact that praying too often might annoy your god so much they'll just kill you.
- If you're extremely unlucky, the game might generate an artifact that is incompatible with your role or alignment on top of the starting staircase, which will result in you being blasted to death by said artifact as soon as the game starts if you have autopickup enabled.
- Using the #name command, players can name monsters whatever they want. If you get killed by a monster you named, their name will be listed in the cause of death. Some names people come up with are absolutely hilarious - just check out nethack.alt.org's list of deaths.killed by a grid bug called YOU HAVE GOT TO BE KIDDING
Funny / NetHack