Here's #2! Click here for the master list!
Whiz Comics #2
This one was close to a cinch, except for the fact that Judge Dredd also made his bow in the 2nd issue of 2000 A.D.
Which character is more noteworthy? Judge Dredd or Captain Marvel?
I think Dredd might have a decent argument that Dredd is more famous than Captain Marvel, but maybe not. It's not a no-brainer, either way.
However, even taking the relative fame levels of each character, I still think that Whiz Comics #2 is a bit more notable, mostly because it maintains a certain level of notoriety in the comic book world that is what this whole countdown is about - issues that come to people's minds when they hear certain numbers, and I think Whiz Comics is one of those issues, and definitely more so than 2000 AD #2.
Whiz Comics #2 also saw the debuts of Ibis the Invincible, Golden Arrow, Spy Smasher, Scoop Smith, Lance O'Casey and Dan Dare (not that Dan Dare)!!
Other notable #2s include the first appearance of the Vulture in Amazing Spider-Man #2 and the first appearance of the Skrulls in Fantastic Four #2.