Standing nearly 2 feet tall, comprised of over 750 individual pieces, and built entirely out of paper...ladies and gentlemen, the crown jewel of my pepakura collection, OPTIMUS PRIME! I built him over my summer break. I got the template for this awesome papercraft model from paper-replika.com. They did an unbelievable job on this thing. It is so detailed that the head alone contains 90 parts. If you're thinking about building this model don't let this picture fool you. My version is only 2 feet tall, but that was after I shrunk the original template by over 50%. If you go by their original template Optimus will be massive.
The template is a free download at paper-replica.com