There are scarier Scarecrows and there are less frightening Scarecrows, but Weasel Cosplay's take on Arkham Asylum's Jonathan Crane, with its sunken eyes and excellently stitched mouth is particularly fearsome. Photo by kashikosa.
This is the Scarecrow from Batman. What I like about this character is how he wears an outfit that fits his alias, to make him appear more sinister. I could implement this into my boss, as it could have an alias, where it will wear a matching outfit.