I kinda flailed a bit when I read that you haven't read any Highlander fanfic, because there is SO much good stuff out there. I don't know if you would be a gen fan, or a duncan/richie fan or a Methos fan... but go forth and read! I sometimes think that I would be really nice to be able to temporarily wipe your memory of stories so that you could read them afresh all over again.

There's a element of where do you start? I'm going to point you here:

Silvia Volk: http://members.shaw.ca/sylviavolk/
Lanning Cook: http://archiveofourown.org/users/Lanning/works?fandom_id=5358
Tessa Rae:http://archiveofourown.org/users/Tes/pseuds/Tes/works?fandom_id=5358

or dive in here:

http://crack-van.livejournal.com/tag/highlander