No secrets here:
When I ran this event, the single biggest thing that influenced my decisions for which mystery materials to give was whether I could find enough for all the teams. I remember once I wanted to give AOL CDs as the mystery item, but I only had 45, and there were 48 teams. I wanted to do junk mail too, but you have no idea how hard it is to get fifty identical pieces of junk mail!
The Evangelist Matthew Inspired by an Angel (1661) by Rembrandt van Rijn
Oil on canvas, 96 x 81 cm, Louvre