I carry a Jetbeam 1aa led light every day. It has high, med and low functions with strobe. When it finally gives up the ghost, or sooner, you never know, I think I might go to this.

http://www.fenixlight.com/ProductMore.aspx?id=79&tid=10&cid=1

I could live with just three brightness levels but 4 will work. Plus the strobe and sos modes could come in real handy.