After a hard day's work bustin' ghosts, who you gonna invoice? The Ghostbusters Invoice above is a prop for the 1989 Ghostbusters II (hurry up and make the third one already, guys!). It was sold at auction in 2003: http://www.shaunusher.com/post/748950961
Previously on Neatorama: 10 Things You Didn't Know About Ghostbusters