Giant Size

Giant Size on Ebay
Marvel Giant-Size comic 69 various titles, May 1974 - December 1975.

Starting in about 1974, for some reason the two major comic publishers experimented with different sizes and format. This was when the Treasury-sized editions, DC's 100-Page books, and this series were released.

Many of Marvel's major (and minor) titles got at least one Giant Size issue, and several got more than one.

In many ways the Giant Size issues are a separate title unto themselves, and are usually treated as such.

Here is a (hopefully) full list of the Marvel Giant Size titles:
Giant-Size Avengers 1-5
Giant-Size Captain America 1
Giant-Size Captain Marvel 1
Giant-Size Chillers 1-3; 1 (two separate #1's)
Giant-Size Conan 1-5
Giant-Size Creatures 1
Giant-Size Daredevil 1
Giant-Size Defenders 1-5
Giant-Size Doc Savage 1
Giant-Size Doctor Strange 1
Giant-Size Dracula 2-5
Giant-Size Fantastic Four 2-6
Giant-Size Hulk 1
Giant-Size Invaders 1
Giant-Size Iron Man 1
Giant-Size Kid Colt 1-3
Giant-Size Man-Thing 1-5
Giant-Size Marvel Triple Action 1-2
Giant-Size Master Of Kung Fu 1-4
Giant-Size Power Man 1
Giant-Size Spider-Man 2-6
Giant-Size Super-Heroes 1
Giant-Size Super-Stars 1
Giant-Size Super Team-Up 1-2
Giant-Size Thor 1
Giant-Size Werewolf By Night 2-5
Giant-Size X-Men 1-2