I often have a lot of windows open, and I grew tired of alt-tabbing a bunch of times to get to the one I wanted, so I wrote sTabby! to solve this problem. My thinking was, when I go to alt-tab, I already know the window I want to go to, so what if I could instead type a key combination to just get to that specific window?
With sTabby! this is easily done. Once the program is started, I can assign a letter key to any window I want to quickly reach. Once that is done, I can just press my hotkey followed by a letter to reach the desired window.