Like others have posted I wear speed stick ocean surf.
The reason? it's the only deoderant I've found that I can wear with breaking out into a rash under my arm. Even other types of speedstick make me scratch all day long but ocean surf doesn't and does a good job (since I don't really sweat under my arms). It also smells good goes on easy, and doesn't flake either.
I don't know why I can't wear other deoderants but I can't. I've given up trying long ago and would rather go o-natur-ale then use anything else.