Not fully 1 punch KO's but 1 punch ended it

http://youtube.com/watch?v=BlS82LC3fTo&feature=related

http://youtube.com/watch?v=wGpu_KU0uY8

A classic by Alexis Arguello. A 1 punch KO of Kevin Rooney
http://youtube.com/watch?v=NGIUQ1mcZ_U&feature=related