Zazu App is a fully extensible and open source launcher for hackers, creators and dabblers. It comes with sane defaults to make it useful out of the box. But everything can be changed to fit your needs. Don't let others tell you the best way to be productive, configure it to be perfect for you.
Zazu was created to be a fully open source alternative to Alfred, but also be completely plugin based. You can remove any functionality you don't like, so if you hate the built in calculator, just get a new one!
Windows, and Linux