I'm sure some/most of you have seen failed SCP's that had pretty good core ideas, but the article it was presented on was usually convulted or otherwise poorly written.
For me, it was around Halloween this year, when someone presented the "Potentially Psychic Wolf-man."
The core idea was that every night on a full moon, this specific man, who was in Foundation custody, would enter a catatonic state in which he could not be woken up from (They tried again with stimulants to keep him awake, which failed.) During said period of time, a sort of "psychic apparition" would appear at the site where he was initially "infected." (For example, he'd be in N. America and he was originally infected in say England.) People in said area would only ever see it "in the corners of their eyes," up until it attacked/killed them. D-class that survived would say it was wearing the same clothing (albeit stretched/torn) as the man in the temporary catatonic state. Kind of a neat variation of the Werewolf, really. Also implies anyone surviving said "attacks" would also suffer the same fate as aforementioned man.
Problem with the article is it started off with "Object Class:Safe EX Euclid Keter", which you can tell is probably going to be a bit convulted. Also made the doctors look like a bunch of bumbling idiots throughout it. Something like "Safe Keter" would have worked. Should have also incorporated silver compounds for suppressing/treating the man.