PC Outline. It's a DOS-based outliner. In 1986, my manager said "Here, you're organised. You'll like this" and he was right - I did. So much so that I bought my own copy. I still use it every day in a DOSBox DOS emulator on Windows 7 and Linux. I use it for passwords, todo and done lists, keeping track of work done for clients, functional decomposition, shopping lists and the steps for configuring and compiling the Linux kernel.