Is it ensure, insure, or assure?
1. The state motto of New Hampshire, which appears on that state's automobile licence plates.
2. A slogan associated with Unix in the romantic days when Unix aficionados saw themselves as a tiny, beleaguered underground tilting against the windmills of industry. The "free" referred specifically to freedom from the fascist design philosophies and crufty misfeatures common on commercial operating systems. Armando Stettner, one of the early Unix developers, used to give out fake licence plates bearing this motto under a large Unix, all in New Hampshire colours of green and white. These are now valued collector's items.