I love to hack URLs to navigate the web, especially for sites with clean urls. What I'd love is if Firefox could hack the address bar text field so that the slash '/' is the default word seperator, instead of the usual space. This way just pressing Shift + Left/Right Arrow would allow power users to quickly select clean url tokens and edit them faster. This could even be improved so that the ampersand '&' is also a tokenizer.
Why haven't I posted this on Mozilla's bug tracker as a feature request, because I don't want to create an account, and I'm hoping that some reader who has one will do it for me :p