I have owned and used pretty much every single GTD app on the market. OmniFocus has been the winner for me simply due to its maturity. I use it in conjunction

I have owned and used pretty much every single GTD app on the market. OmniFocus has been the winner for me simply due to its maturity. I use it in conjunction with org-mode for Emacs. org-mode is what I use for managing my code and computing environment. OmniFocus is bigger picture: "Call so-and-so @Phone" I have to also drop my hat in the ring for TaskPaper. It's quite well done. However, OmniFocus is unfortunate in the sense that you cannot export a flat file. It also is unfortunate how big of a behemoth the iPhone application is. I wish they'd include a standalone quick entry application so I don't have to load the entire database every single time I use the app.