"Code 12" by May Day Girl-Save-Our-Ships is a favorite of mine. It's only two chapters long, but it's a sweet take of Pacifica's relationship with the Pines after "Northwest Mansion Mystery", and it's very well written too. If the show itself doesn't do another dedicated Pacifica episode, I'm willing to see this as my own personal headcanon.
Razzin-Frazzin Robot
Here's one I'm working on. It's a series of one shots about the henchmaniacs.
Razzin-Frazzin Robot
![[up]](https://static.tvtropes.org/pmwiki/pub/smiles/arrow_up.png "[up]"){kind=icon}
Are you referring to mine?
Gravity Falls: Deep Woods, is looks to be off the good start. It's a completely fan created animatic form season 3. They have about 30 to 40 people working on it on their own time, and have been it production for over a year. They have first part of Episode one, which takes place after Stanchurian Candidate, out so far, and have almost finished the second.
Blog: https://gfdeepwoods.tumblr.com
Episode: https://www.youtube.com/watch?v=XPasWS_qEf8
They are always looking for new artists and animators as well, including someone to finish the last scene of Episode 1 part 2.
Queen Of Overanalyzing Media
Fisherman's Knot http://archiveofourown.org/works/6179098/chapters/14157307
One of the best fanfics I have ever read. Currently trying to edit a page for it.
Monkey See, DIC Do
Apologies for necro-ing this thread, but I found this pretty good Gravity Falls fan fiction (currently in progress) called Embers and Ashes. It is a sequel to another pretty good fan fiction (which is complete) called Arrogance of Power, in which Pacifica meets her ex-beau in the fiction Dipper in (where else) Gravity Falls after some...really bad things happen. This fic takes place six years after the summer in which the show itself takes place in.
https://www.fanfiction.net/s/12777850/1/Embers-and-Ashes
Since Gravity Falls doesn't have one, I'd might as well make one myself.
Feel free to discuss, chat, and post ideas here.