Higurashi (no Naku Koro Ni) is pretty awesome. Murder mystery + time loop + deranged lolis + madness. It's finds the line between being cryptic and not making sense and it plays hopscotch with it. Pretty wonderful.
Umineko (no Naku Koro Ni), the sequel, is currently airing. It's ... well, I'm waiting to pass judgment on it until it's done, but it's gone way past that line and is in the land of the absurd, which is pissing me off. But, like I said, withholding judgment.