If a printer doesn't need toner, ink or copy paper, is it still a printer? Well, I guess if a bear still shits in a forest, then yes. Using plastic paper, it's a very green (and pricey) way of printing.
The PrePeat RP-3100 paper is actually made from PET plastic, which means it can be reused up to 1,000—so once your printed document is no longer needed, it can be inserted back in the printer, where the line thermal head prints the ink-less words on again.
However eco-friendly it may be, there are some major downsides to the PrePeat RP-3100. It only prints in black and white, and costs a whopping $5,600—which each sheet of plastic paper costing a further $3.35. Each. I guess you don't need to buy ink for it, but that $3.35 price does sound astonishingly high. [Sanwa Newtec via Crunchgear]