Your first comic book.
This is a bit of a cheat because this is territory that I have already covered. Regardless, what I consider my “first comic book” is actually three, and I call them my first because they were the ones that I bought with my own money, and they were the ones that started me down the path that over 30 years later I have never strayed from–not even for one month! I love comics almost as much as my family. ;)