This page lists NH4 bugs that were unbalanced, crazy or weird enough that we may some day want to add a (nonscoring) option to bring them back (so that people who missed them first time can relive them).

* Defence starting at 10: We changed from AC precisely because it was so unintuitive, but we're still using the AC scale internally, so things like this can happen. (It happened at /dev/null/nethack, too, with the bobble hats.)
* Generalized artifact naming: Turns out that for quite a while, you never got the "finger slips" message when trying to name an item to match an artifact: if the item had the correct base type, you just outright made the artifact. Sure, we don't directly have the artifact naming exploit any more, but…
* [ticket:900]: this is actually pretty funny, really (a case where a tame monster has an attack that hurts its owner, and which sort-of makes logical sense).
* The infamous "red question marks" tileset. This could actually be scoring, given that it confers no advantage to the player and is entirely client-side.
* For a while in Fourk, bones levels from DL20 or later in the main dungeon, if they were not special levels, would be saved as if they were from, and subsequently loaded at, dungeon level 2.