Related tools
Fixers for specific hijacks
Google stop focus Greasmonkey script
Free Control Firefox add-on (abandoned)
Slash Preserver Firefox add-on
Save Slash Greasmonkey script
Firefox’s built-in protection
In bug 380637, Firefox added an option to block pages overriding keyboard shortcuts. It’s under Page Info → Permissions or about:config → permissions.default.shortcuts. Using that option, unfortunately, breaks Escape to close built-in popups and tab navigation with Home and End key, while not saving the Slash key.
More general
Disable website keyboard hooks Greasmonkey script
Vimperator Firefox add-on is defunct but lists alternatives