But my top What if's of all time are What if #105 and 114.
105 is of course the What if that launched the (Amazing) Spider-girl universe. A universe that I honestly loved all the later parts of like the Fantastic Five, J2, Wild Thing, A-Force, Buzz and so forth.
114 is especially the hidden gem.
Showing a world where the contestants of Secret Wars never made it home.
So like in Spider-girl we got to see a whole new generation of superheroes step up and luck out getting "home" to Earth in the end. It was a great story and apparently there was talks of it getting a series like Spider-girl afterwards but nothing came of it which is a shame as it's a universe I'd LOVE to see revisited.