I used Vimium for a while, mainly for the feature of opening links with the keyboard. But I never stuck with it, forgot to use it, because I really don't like the mode-switching and having it default to taking over keyboard input.
Finally found Link Hints, which does only the link opening part, but better (IMO), and with normal keyboard shortcuts. Now I'm constantly using it.
Modeless Keyboard Navigation[0] is a fork of Vimium by an RSI sufferer that doesn't have the mode switching element (but does keep all the other actual features); instead you use Control/Alt + whatever key combinations. Basically it's like Link Hints but with more shortcuts.
Finally found Link Hints, which does only the link opening part, but better (IMO), and with normal keyboard shortcuts. Now I'm constantly using it.
https://addons.mozilla.org/en-US/firefox/addon/linkhints/