If you enjoy Ever17, 999: nine hours nine persons nine doors (inb4 I ordered those objects wrong) is probably up your alley as well. I've heard good things about YU-NO as well, though I've never played it. Oh, and Chaos;head does have some decent horror stuff sometimes, it's set in the same universe as steins;gate, but largely unrelated (and s;g has slightly more believeable technobabble...).