My weekend project. I run Windows on my Macbook Air for development and pressing Ctrl+C, Ctrl+V for Copy/Paste kills my pinky and messes with my brain when I switch to OS X, so I made MacWinKey to swap the Left Control and Windows Keys. This lets you use Cmd+C, Cmd+V for copy/paste, consistent with OS X.
Uses a low-level keyboard hook to inject the correct keys, so no reboot required.