A fuzzy search. Very useful when grepping or ls-ing large directories or large results to then have a search query to narrow down the results further and browse the results.

Very useful for providing a menu to search. Used on my system for basic system controls.

Very useful for providing a menu to search that is comparable to the start popup menu on Windows XP. I use this for launching common programs as well as launching browsers to a particular page so I have a browser-agnostic bookmark system.