Good old Hexen and its Add Ons. Me and my friends played this for hours and hours killing each other, playing COOP ect. I think the atmosphere survived the ages, but for some reason the gameplay/graphics feel so poor I cannot bring myself to go back and play it again... yet Duke Nukem and DOOM I can easily play again.
This game was not made for those faint at heart. It was difficult, dark, and strange. You can get stuck on some level for hours that would normally only take 10 minutes because they would hide buttons, hidden triggers, or just the requirement of killing a monster hidden behind a glass window you can only shoot from a distance.
The three chars to choose from are very very different and add a interesting element to the game that old school games really didn't have. I would only get it for Nastagia, for those that never played it... you will not like this game.