Skein
A hash function submitted to the 2008 SHA-3 competition that reached the final round but did not win.
Skein was submitted to NIST in 2008 by a team led by Bruce Schneier and Niels Ferguson. It made the final round in 2010 alongside BLAKE, Grøstl, JH and Keccak. The design uses Unique Block Iteration (UBI) on top of the Threefish block cipher, so the same primitive both encrypts and hashes.
Keccak won in 2012 and became SHA-3. Skein is remembered as a well-engineered design that lost to a competitor with a simpler story. Its flexible output length makes it a useful case for anyone comparing UBI with Keccak's sponge construction.