I've been on and off the GTD (Getting Things Done) bandwagon and my excuse, at least to myself, has been that I've yet to find a good tool that works for me.
Last week I found iGTD, a native Mac application that appears to do everything right. An uncluttered yet functional UI; keyboard shortcuts for everything; integration with QuickSilver hierarchical projects; notes and everything you could wish for..
But most of all, it just works.
Highly recommended for you list-makers, GTD faithful and everyone who wants some sanity in their cluttered lives.