A trash-cleaning Rube Goldberg machine, part of GISHWHES 2016:

"Time-lapse this submission to 20 seconds or less. Create an elaborate Rube Goldberg machine that ultimately serves an an incredibly simple function. For example, you could set up a Rube Goldberg machine at a deli counter in a grocery store that, upon completion of its entire elaborate multi-step process, issues a single numbered ticket to a patron waiting for their turn. The machine MUST be set up in a public place."