Here's #7! Click here for the master list!
Crisis on Infinite Earths #7
#7 is surprising in how few notable issues happened at that number.
New Gods #7 was "The Pact," which detailed the origin of the current situation between Apokolips and New Genesis, and the whole "Scott Free swapping places with Orion" story, which is a big part of New Gods history.
The very first Neil Gaiman Sandman storyline ended with Sandman #7.
Amazing Spider-Man #7 was the first time a Spider-Man villain returned (the Vulture, by the by).
The Fantastic Four and the Justice League of America are noted in how UNnotable their seventh issues were - really lowlights, actually.
The most notable issue other than the one representing this number would be Daredevil #7, which was the first appearance of the Wally Wood-designed red costume for Daredevil. That's a big part of comic book history, but I think that the seventh issue of Crisis on Infinite Earths - the death of Supergirl, stands out a bit more, mostly due to:
A. The shock of a major character dying like this
B. The famous George Perez cover
Those two combine to make this a comic that continues to be referred to over and over again - heck, we were just discussing it a month ago, vis a vis the Perez cover (which has been homaged a lot since then).
So that's the pick.
Name me some other lucky sevens!!