You can use it to whom you are respecting or esteeming, or to someone is higher status than you are (though this concept is pretty classic), or when you write his/her name next to the destination address on a physical mail; it means you can write thire names without "sama" inside of the envelop if you want. Also people usually write someone's names with "sama" everytime they write people's names on business emails.

The previous answer explained it all =) I think many people like to use this term when you admire someone. I would say トニー・レオンさま as well: one of world hottest Hong Kong movies star. haha!