how about Directory Opus? sure, it's a file manager and not a tweak program. but it is 95% customizable. you can make your context menus look however you want them to look - they can even differ by filetype or even custom filetype groups (like images or archives). all toolbars are also customizable, and can be moved about the screen as you like. you can incorporate 3rd party apps too - for example, i can select files and click my Burn button to send them to ImgBurn and start recording a new data disc with a single click.
regex rename scripting, duplicate file finder, file splitter/joiner, integrated ftp, dynamic thumbnails, custom tooltips, custom status bar, custom themes...
no single app has increased my productivity more than Opus. it's pricey, but it's worth every penny!