I have an interesting 1982 Wayne Gretzky Gateway cover from when he broke Phil Esposito's single-season scoring record. Gateway produced 2,000 covers, but Gretzky signed most of them in the area where the cachet was supposed to go.
The full story behind the cover is on dealer Steve Ciniglio's flyer from 1994, an image of which is included along with the cover. At the time, I paid the issue price of $40.00; I have no idea what its current value is.