Tell us about your favorite writing project/universe that you've worked with and why.
It all depends. I absolutely adore the chrysopoeia world which spawned from last years Mini NaNoWriMo, it is original Steampunk and actually a continuation of an idea I had a while back about a single mother who also happens to be working as an assassin. Original title for that was "My mother writes letters and kills people" and it was supposed to be written from the point of view of the daughter, Celia, starting just as she was starting her first year at a boarding school. I ended up ditching that idea, or rather reworking it into what was started last November and still needs an end. I liked the "write about 200 words aday"-format and at the time compared it to webcomics in a way. Except without images. So yeah, I still have a lot of love for that world and the characters it spawned and I have a plan to write one short story for each of them, including Celia. I am also rather enamoured with the mythology for ghosts that I dreamed up and the city Crysopoeia itself and the Gods and... and...
Moving on
When it comes to fanfiction my favorite 'verses are two - The Good Boy 'Verse and the Leverage AU I wrote for last years Leverage BB. The Good Boy Verse is because for some reason the words really flow when I write about Hugh and his pet and I am sure some psychologically inclined person could draw all kinds of interesting conclusions from the fact that I mostly write from pet!Taylor's POV and such but I just care about how the words flow and how alive the world feels when I think about it.
As for the Leverage AU (found
here), it is the longest piece of writing that I've actually finished. Don't Stop is approaching it in actual wordcount but that's not finished yet so it doesn't count. I am also very pleased by the faux science I put into it and all and all how the story came together.
Of course when I am in the middle of writing for a 'verse I am very in love with it. At the moment the unlikely trio(Eliot/Sterling/Nate) take a pretty large part of my brain but in a month that might (hopefully) have changed to the two Big Bang stories I am writing this summer.