Get invited to brawl at Brawl'gar Arena in The Valley of Honor in Orgrimmar.
The First Rule of Brawler's Guild
You Are Not Your $#*@! Legplates
The Second Rule of Brawler's Guild
Brawlin' and Shot Callin'
A loud musical tune with choral elements plays when a character earns this achievement. Everyone near the character that just earned the achievement hears it, too. >_<