Yes, very tough...

Keeping in mind that my MMW collection isn't as comprehensive as most on this board, I choose in alphabetical order:

Amazing Spider-Man Vol. 2
Avengers Vol. 1
Captain America (Silver Age) Vols. 1 & 2
Fantastic Four Vols. 5 & 8
Thor Vol. 3
Tales of Suspense Vol. 2
Tales to Astonish Vols. 1 & 2

The upcoming TPB release of Thor Vol. 4 would certainly crack this list as would Iron Man Vol. 3.  But I don't have 'em yet.......Wink