I have two...the two most deliberate headbutts i've ever seen... 1) Ruiz-Johnson...for those of you saying Ruiz faked low blows...after the 3rd or 4th one...Ruiz was PISSED. he got close to Johnson and flung the most deliberate headbutt i've ever seen...Ruiz wasn't going to take any more of that lowblow crap. 2) Golota-Nicholson...I wish i had a tape of this one...Golota, from a distance, flings himself right into Nicholson with a headbutt...he actually stepped into it like a punch
The accidental headbutt that ended the Gainer marathon sprint against Marquez. I believe that Larry Merchant even proclaimed it to be the greatest accidental headbutt of all time.
I second thewoos choice. In fact Holyfield has without doubt been the most cynical user of the headbutt as a weapon. Lewis said it and Tyson said it after they fought him, that he headbutts in a deliberate attempt to harm his opponent. It is a illegal weapon but it is hard to punish, if it looks accidental.
The headbutt B-Hop landed flush on Taylor's jaw in their first fight was an absolute classic. I'm surprised Taylor wasn't badly hurt by it. It rattled his jaw something terrible.
Terrance Cauthen vs Raul Frank Frank landed an accidental head butt and knocked Cauthen out with it. http://www.boxrec.com/media/index.php?title=Fight:1166153
A couple come to mind...Golota against Bowe in their second fight, and Butler in his fight against Grant.
Golota had Bowe almost ready to go, but he intentionally headbutted Bowe, opening up a massive cut above his own eye , was deducted a point and allowed Bowe much needed time to recover.