1. A small slotted (3/32") screwdriver made by Xcelite and having a green handle. Required for the screws on a Switchcraft A*(M/F) connector, as well as many of the same uses of a diddlestick.
A "Reddy" ("reddie"), named for its red handle, has a slightly wider tip (1/8") than a Greenie.
2. A slang term used by NY rental houses to describe some Altman 360/360Q fixtures whose lenses had a slight greenish tint to them. See this post.