What are your favorite comics from Marvel that aren't collected in trades?
For me, it has to be Silver Surfer v3 (1987). The first 18 issues are in the Essential Silver Surfer volume 2 but you have to hunt down the singles to read any further of this 140+ issue series.
Fabian Nicieza's Gambit series from 1999.
And the entire Marvel Graphic Novel series. I would love to see a collected edition of those.
Edit: Might as well include Out-of-Print books as well. So what out of print stuff would you like to see receive a new edition?