Agatha Christie's And Then There Were None is a classic "who done it?", although it probably won't scare the crap out of you.
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this one that I posted about yesterday... it's similar in construction to And Then There Were None and I'm finding it very well done. Even a little scary.
If you enjoyed the CSI games, you might also like the Law & Order games.
I can think of some scary games, but not necessarily with the "who done it?" element. The Gabriel Knight games sort of have both (especially GK2).