Hexen! I have a kinda love/hate relationship with it: obscure puzzles, tanky enemies, less weapon variety than Doom/Heretic, devilish enemy placement...

But I still love it. Its' atmosphere is just special, the feeling of exploration, and Wraithverge...

The first stage (not the tutorial one) is shit though. I almost dropped the game during it but fortunately I managed to stick to Hexen. The second and third stages are peak. That swamp...