Replying to Best promo items for my new website?

Hello, I just started a new website called riding backwards. (www.gnidir.com or www.ridingbackwards.com).  I am trying to get members to join and I am going to offer insentitives to people who refer others.  I am deciding which item to give to a person that refers 10 members.  The choices are 1.  Shot glass with our logo.  2.  Bandana with our logo.  3.  Foam koozie (beer sleeve) with our logo.  Tell me what you think is best.