Heretic II Abode
Ogle: The Return of Morcalavin
a single-player add-on
The Heretic Fortress (THF)
a multiplayer mod
The rotating cylinder in "Cliffs of X'chekrik" sometimes gets stuck, but if you move around the map, you'll retrigger it.  I've gone to great lengths to avoid this, but alas it's not perfect.
The "Ogle Vigilante" map pushes H2 to its limits, but nothing (that I know of) disappears and an overflow error only occasionally shows when the map first loads.  Sometimes the weapons' sounds turn into Ogles singing, which is REALLY bizarre and I can't begin to understand why that happens.  If that happens to you, the only cure is to finish the map.
***If the game crashes when you try to save a new config, you can simply press Esc without saving.  Alternatively, you can copy a config you made/make in normal Heretic II from Heretic II/base/config to Oglequest/config and then load it in the game (which should automatically save it as your default config). Either way, you must exit the game first before playing; if you don't, the Ogle player model will show up as Corvus and the in-game messages and sounds will be drawn from the original game when they shouldn't be!