The Sargosian Abyss
The Sargosian Abyss is well-named. It seems to pull you into some dark depths, right from the introduction. It has stricken me with its incredible, almost tangible atmosphere. I've always preferred ASCII in roguelikes, thinking that no graphics can evoke that arcane ambience of glowing letters on a black screen. This game has proven me wrong. Its strange colors, its melancholy music, its vivid and haunting writing; these things conjure that eerie other-wordly mood of shadowy dungeons and forgotten altars, as only a few works of art can. A true roguelike aesthetics.