SCP was a great rabbit hole, until I took some psychedelics after I'd been reading it during my downtime at work the previous few weeks. I spent much of the trip seeing the face from SCP-87 [1] bulging through the inside of my eyelids.
SCP is an real mix between "Agents of SHIELD" type weirdness and the occasional truly disturbing nosleep material. I dig into it every now and then but usually stop when I read something I'd rather I hadn't.
I haven't been able to enjoy browsing it since.
[1] http://www.scp-wiki.net/scp-087 (bottomless staircase below a school)