Um... I go on crazy binges of Harry Potter fanfiction every now and then but otherwise no other fandom has tempted me (though I can't rule it out, it's just.. not yet). Time Travel fic being my favorite, Slash second and lately Dark Harry. Combine them
I knew a girl that wrote fan fiction... 20 chapters of Harry Potter fanfiction... Maybe I just don't get the appeal of reading things based on another person's characters that have no relation to the actual story. I think I saw an episode of Strongbad about that lol so to me, fanfiction is like watching fillers that never existed and since it carries no weight I'm not interested. :/
If doujinshis count, then yeah I do. Otherwise, no. I've found one doujinshi that rivals the original work in depth, and possibly another that I haven't read yet. Most written fanfics are terrible though. Terrible enough to make you want to dismiss the entire art form.