The one that I've been using for everything for the past decade or so is an Eagle Creek product called the Ultimate Travel Strap (I think). I haven't seen them anywhere in a long time, so I don't know if they're still available. Great padding, nice contour, non-slip texture. I move it from my daily messenger bag I carry to work, to my Briggs & Riley briefcase that I carry for biz trips, to a bigger Air Boss-like carry-on, to just about everything else that I carry on my shoulder.

The straps that come with certain Briggs & Riley bags are really pretty nice too. Not as thick as the one I mostly use, but they have good grip, and a nice little stretch to them which increases the comfort.