Z Angband/YMMV

• Game Breaker: High mages gain new spells at a much faster rate than other spellcasting classes. Combined with the experience bonus from trying new spells, a human high mage can gain levels extremely quickly after a lucky start.
• Nightmare Fuel: Z Angband isn't a horror game, but it definitely has a nightmarish feel to it on occasion. Firstly, many of the regular monsters are some of the weirdest to be found in a roguelike; eyes, blobs, worm masses that self-replicate, floating lights, mushrooms... secondly, the dungeon levels are huge, empty and dark. You can't see anything unless you have a light source, and almost every room you visit is empty. Thirdly, there's the wilderness, which is an enormous area between towns, in which you may find monsters who may be incredibly high level compared to you... and if you're caught in the wilderness, the nearest safe town could be miles away. And for the scariest experience of all... try crossing the wilderness at night, when you can't see more than a square in front of you.