The most common thing I saw this year was girls making skirts out of broken inner tubes. (This happens a lot when you have a lot of girls who are on a field reset crew you are on and we are given the ok to destroy the broken tubes after you all pop them in battle.)
Since my start in FIRST in 2001, I've noticed the one common thing among teams through the competion season is always something with the game item, so in this year tubes were the common item to "play" with while waiting for matches, and at other times when there were lulls in activity.
This is true of every year, and most often observed while on Field Reset crews.
We have fun doing field reset, and each try to out do each other with the game elements in a fun way while waiting on matches or any time really.
2007 - Tube skirts, or using tubes as seats in the pits, sumo tube matches.
2006 - Dodgeball with the Poof balls or juggling them, spinning them on your hand.
2005 - Stacking of the tetras in unique ways, carrying people while sitting "in" tetras, seeing who can fit in a tetra.
2004 - Sitting on the balls or playing volleyball with them.
2003 - Sitting in or on the bins, making Bin-Person costumes, or remote control bin robots.
2002 - Playing soccer, or just doing some tricks (ie: juggling (by foot or hand))
2001 - More juggling, kickball, and tossing the 2 different size balls around.