The Myrmidon by @Moreau , 'cause, gosh, that was just my all-time favorite WiP. Hands down. (And one of the ones that finally convinced me that I should suck it up and try and actually talk on the forums instead of just dance around from subject to subject quietly in awe of people’s talent, and shying away from ever participating in any of the discussions myself).
But, yeah, amazing writing, fantastic plot, great characters, marvelous worldbuilding, (not to mention glorious drama)… and the last post was on September of 2016.
And none of this is even mentioning the copious amount of puns in the thread itself… So. Many. Puns.
It was beautiful.