Ever since I saw a guy on the street using this gorgeous, huge (6-8") old-fashioned skeleton key as his key ring, I've been dying to find one for my own use...
From sets like these, except longer, and more ornate!
http://www.etsy.com/listing/95096934/vintage-keys-french-metal-heavy-iron-art?favorite_user_id=11087275&show_panel=true