Original von Scribbler
Well, suddenly I can only recall one off the top of my head (because it was the only one keeping me from migrating from Mozilla FF altogether) is mouse gestures. I know some people aren't fond of them, or really care about it, but I find my surfing oh so much more relaxed when I can use simple gestures to navigate.
It's already there in KDE 3.2. See:
http://developer.kde.org/development-versions/kde-3.2-features.html
(search for KHotKeys)
Other resources:
http://datschge.gmxhome.de/khotkeys.html
http://ktown.kde.org/~seli/khotkeys/