There's polypropelene (know as poly prop) used for all sorts of pipe & fittings - mainly in blue (for potable water), yellow (gas) & black (landfill, dirty water). This plastic is also used for various styles of plastic stackable chairs. But where it appears in the top ten, I don't know. Good luck!
I would be surprised if the No. 1 isn't polythene (polyethylene). Closely followed by polystyrene. Even the most cerebrally-challenged McDonald's-age chav must recognise polystyrene.