crapehanger\ KREYP-hang-er \ noun
1. a person who sees the gloomy side of things; pessimist. Also, crepehanger.
Origin: Crapehanger is an Americanism with roots in the custom of hanging crepe paper as a sign of mourning. It came into popular usage in the 1920s.
New word to me, but I certainly know a lot of people who could be described with it...sometimes myself.