The 7" scorpion was created out of one uncut square of Korean hanji paper.
This is an example of "hex pleating," a design technique analogous to box pleating, but that uses hexagonal symmetry.The 5" tree frog was folded from one uncut square of Origamido paper. Many more at the artist's website. (via k9pincushion)
Reposted from 2008 (!) to add this super-awesome recent example:
Via, where the artist notes "It took me 3 months to design and fold this origami samurai from a single square sheet of paper without any cutting."