(Re-)Visiting the Mysterious Side

[Sky]

I've realised that after watching Higurashi no Naku Koro ni, getting blown away by the ending of School Days, reading What Evil Lurks by Greg Taylor, and His Lordship Chaos' The Paranoia Groove, and 1101 and thinking about re-reading Schools United (I'll solve it one of these days) that I've taken a distinct slant to my watching and reading, so I'm looking for recommendations along those lines.

(I'll admit that 1101 isn't really a mystery, but the reader spends a lot of time trying to guess what the hell happened...)

I'm fairly liberal in my tastes, and I don't mind darker stuff or thrillers, so feel free to suggest any Ranma or Sailor Moon story along those lines that fits.