Speaker Mar'grom
Speaker Mar'grom is a rare ogre that can be found at any of the 4 ogre camps in Blade's Edge Mountains. He is reported to spawn around Gruul's Lair more then any other location. Since he kind of blends in with the other ogres I'd recommend making a /target Speaker macro. Also, you can farm any of the 4 ogre camps while you wait for him to spawn.
Don't forget, every 10-15 minutes be sure to mount up and check for him. Also, to note he will NOT spawn in the mine with ogres in it in southern Blade's Edge.
Speaker Mar'grom Spawn Locations