During their reign? Seem's nowadays that fighters fight out of Las Vegas and rarely travel, but what Champions can you recall of that would fight anyone, anywhere? You know, they'd say "I'll go to his back yard" and actually do it? I know one of the privileges of being the champ is having home advantage, but which ones didn't care about that and were still road warriors? Lennox Lewis springs to mind when it comes to modern fighters.
Hilario Zapata, Saoul Mamby. It wasn't all altruistic. Champs would often get big money to fight the local hero. Mamby got some huge paydays - Of course, Don KIng probably got most of it.
There's more though. Muhammad Ali fought in Kuala Lumpur Malaysia, Kinshasa Zaire, and Manilla in the Philippines. He was as game as they come, don't forget him beating George Chuvalo in Canada twice.
I'll give props to Froch, despite when discussing a rematch with Ward, he'd pretty much fight anyone anywhere, and did! GJ is an excellent shout McG
Lorenzo Parra Check out his schedule once he won the title http://boxrec.com/boxer/43081 Alexis Arguello http://boxrec.com/boxer/2179