Like others I have all my wristbands etc since 2009, my Coldplay bracelet, free presses from over the years and crew tee shirts.
My best finds are from the Live at Worthy farm event. One is a laminated sign from a container that had all the electrical cables etc for the area that Haim were and one of only 3, I think, Glastonbury free presses that were onsite for the event. I got this from staff canteen as a birthday present on the Saturday after Coldplay’s gig on the Friday night.