A lot of shows give exhibitors something to remember the show by.
Could be just a show button, but many give other things. I've gotten ribbons, refrigerator magnets with engine/tractor photos, aluminum plaques, bass plaques, and even bronze castings.
The european shows are great for giving real nice bronze castings and plaques to exhibitors.
The two nicest ones I've gotten in the States are from the Edgeta National show in 2008 and the Edgeta NW Regional show in 2009. I'll post pictures of them later.
Maybe some of you could post pictures of some the nicer ones you've received.