Collar Clips from Migardian Treasure in Gravesend, England makes collar clips in a variety of pop-culture motifs, some obvious and some very subtle indeed:
Captain America shields, Captain America stars, Hawkeye and Hydra vs SHIELD; Boba Fett, Vader and Stormtroopers (also available as brooches and earrings).
(via Geeky Merch)