What is the best item to be given as a giveaway?

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I'm thinking about button pins but is there another thing or item that you're going away for your friends as a sign of friendship and TO SAY THANK YOU for the help they have rendered with me in a major event. They do have T-SHIRTS from the main organizers, me as the middle man also wants to thank them soooo much for their presence. There are 52 of them in total. Anything in mind aside from keychains or button pins? Thanks :)