-flux capacitor (classic FIRST prank)
-any number of items from this video:
http://www.youtube.com/watch?v=MXW0bx_Ooq4
-Turbo Encabulator (
engineering joke, also from the above video)
-sonic screwdriver (Doctor Who)
-nanites
-nanotubules
-buckyballs
-some [element] (try xenon, astitine, or anything that you could pass off as "just a material")
-an "LHC"
-a previous FIRST game piece
-a large "black bag"
-something in a different language
And if the announcer will let you...
-an easy button (you can actually buy these...)
-chloroform
-a very very large bucket
Any other ideas or things people have done?
