I just finished up designing the pins that will be awarded at the Feb 5th event I'm hosting as RIW Hobbies in Livonia. I think they're a fun play on the "I Love New York" logo. From my experience players enjoy having some type of take-away that says they won an event. So I try to create a unique pin for each event I run.
The pins are created by printing this pdf onto inkjet shrinky-dink paper. Once the pins have been shrunk I attach pinbacks (you can get these at any arts and crafts store) and seal them with an acrylic spray.