Here's #3! Click here for the master list!
All Star Comics #3
This is a tough break for poor Otto Octavius, as he made his first appearance in Amazing Spider-Man #3, and he is a pretty darn important comic book character, but all said and done, I think it is pretty clear that when you think the number three (which is a magic number, don't you know), you think of All Star Comics #3, the creation of the first comic book "all star" superhero team, the Justice Society of America!
Are they the first superhero team PERIOD? I forget.
Anyhow, in this issue, Gardner Fox turned a bunch of solo adventures (All Star Comics was an anthology featuring stories from National Comics as well as All-American Comics) into the debut of a new superhero TEAM, all through the use of a clever framing device!!
So this definitely stands out at the definitive #3.
But there have been plenty of notable #3s over the years!
Here are some (I am sure you all will have more to share)!!
X-Men #3 debuted the Blob!
X-Men #3 (1991) was the last issue of Chris Claremont's SEVENTEEN YEAR run on the X-Men!
Fantastic Four #3 was the first appearance of the Fantastic Four's costumes (and their Fantasticar!).
We3 #3 was the last issue of that awesome mini-series, and it was AMAZING! "No de-com-mish We3."
Quasar #3 pitted Quasar and the Human Torch against the dreaded ANGLER!!!
Marvel Premiere #3 was the beginning of Doctor Strange's second shot at a series (which soon became Englehart and Brunner's classic run)!
That's alls I gots!
Feel free to name some more!!