The most famous instance of one horse trying to 'savage' a horse whom he can't get past is the 1980 Tremont S, which was immortalized by the NYRA award-winning photo. Golden Derby had a lead and wasn't knuckling under to Great Prospector's run, so GP snaked his head around with teeth bared. Great photo. It is titled "The Savage", image should be available somewhere.
In fact, I found it here:
http://marketplaceadvisor.channeladv...226&i=15277414
Some TB's are so competitive that if they can't run faster than the other horse, they try to intimidate it into submitting.
PS. GP's sire, Mr. Prospector was a hyper-competitive horse who also tried to enforce his position with his teeth on more than one occasion, according to an elderly gentleman I know, who witnessed many of his races. Mr. P's biggest contribution to the breed may have been his will to win.