I, Sylocat, officially signed up on Wikipedia in late may of 2005. I am an anime fan, and a film buff (sort of), and frequent the pages of films and anime I like. I have done a fair bit of editing of pages. I mostly specialize in cleaning up spelling and grammar mistakes, correcting factual errors, or helping to better organize the layout of information on the pages, but I have also done quite a bit of original writing and adding to several pages across the site. I also vote on whether to keep or modify articles in the talk pages. I am generally inclusionist on such issues, believing that many things are important. It's impossible to form concrete rules as to what is noteworthy and what isn't, and that's as it should be, the only question is how we interpret it. I personally believe that too many articles is better than too few.
Although most of my writing contributions to pages have been rather small (I've done quite a bit of contributing in general, but that's in the form of a bunch of little edits on a lot of pages), I do have two rather large accomplishments to my name here:
1. I started The Right Stuf International's Wikipedia page on my own. They are my favorite anime retail company and I was surprised that they didn't already have a page, since ADVFilms already did, as did several other retailers. Thanks to whoever came onto the page after I started it, and expanded it for me.
2. On the page about Prester, the fictional world in which the anime series Last Exile takes place, I singlehandedly created and wrote the entire "History" section on the page, detailing everything I learned about the backstory of the series, using info gathered from the series itself, an online interviews with the series' creators at GONZO, and a translation of the series' artbooks (which unfortunately have yet to be officially released over here, which led to wiki editors accusing me of fancruft, but who cares).
Anyway, that's not much, but it's what I've done so far, and for what it is I'm proud of it. I'll be adding to this list as I do more stuff.
3. Since writing the above, I have started and written the page for physician/serial killer Michael Swango, and I think I did a more thorough and a neater job with that one.