Today, I'd pick...

Sgt Fury 2 -- reading #1 right now and it's a riot: great combo of story and art, with hilarious wise-cracks surpassing the best of Spidey (the latter merely commenting on beating up baddies, while the Howlers were howling bout actually killing Nazis, tons of them)

Thor 7 -- the four-part Mangog/Ragnarok saga is my favorite Thor story, the era's Galactus Trilogy of Asgardian arcs

Warlock 2 -- another favorite classic: Avengers Annual 7/Marvel Two-In-One Annual 2 -- Thanos in a cool, concise, cogent conclusion

Defenders 1 -- for their first couple years they really were Marvel's top team; in the summer of 73 they beat the Avengers (as a kid I kept careful tallies on each individual battle in the "War", and the non-team won decisively)

Tomb of Dracula 1 -- one of these days it will be reprinted in color; in many eyes the series gets better and better as Wolfman/Colan hit their stride, but I loved the Conway origin issue

I would also love to see FF 11 (Hulk vs. Thing, Doom vs. Overmind) and Human Torch 2 (to read for the first time a whole Silver Age book of Thing team-ups!)