A gamecock is a scrappy rooster whose temperament lends it to cock fighting. Cock fighting is illegal. Still, South Carolina seems inordinately proud that their mascot is a chicken. Foghorn Leghorn is not a gamecock.
Wikipedia: A gamecock may undergo physical conditioning in preparation for a fight. The conditioning process is sometimes referred to as a “keep” and is designed to, among other things, tame the cock so that he can be handled during a fight.
The most famous gamecock in contemporary times is Little Jerry Seinfeld, the gamecock featured on a notable (and hysterical) episode of Seinfeld.
Kramer: “Just because big Jerry is a has been doesn’t make little Jerry a never was.”
Ultimately, what else is there to say about gamecocks? They seem to be angry birds who run around trying to fight and f**k everything they see. I leave you with this: