Box
a welded metal box hidden in plain sight (2007)
The assignment for Chris Csikszentmihalyi's class "Other Product" was to make a container and put it within 2 blocks of the media lab outside somewhere and you couldn't affix it to anything. Container that stayed there longest won.
I welded together this little green beauty out of 1/8" inch stainless steel; painted it and placed it over some exposed pipes on a concrete slab next to an electrical box on the sidewalk. It stayed there for 6 months until construction workers removed it while fixing the electrical box next to it. (I won, bitches.)