A PIG!
File:Collared Peccary.jpg
Full examination results finally published in Scientific American, Dec. 16, 1927.
Nebraska Man turned out to be neither an ape nor a man. It actually turned out to be:
Info Source:
http://creationwiki.org/Nebraska_Man
The tooth genus of Peccary called Prosthennops and its identification as an ape was retracted in the journal Science in 1927.

Image Source:
http://commons.wikimedia.org/wiki/File:Collared_Peccary.jpg