Especially the first ones gifted to you by other people?
Batman #493 "Red Slash", in the middle of the Knightfall arc.
Uncanny X-men 175 "Phoenix" by Clermont just as a fluke at a garage sale. The family let me keep it no charge.
Astonishing X-Men #4 - Holocaust! by Lobdell. Really confusing if you only watched the cartoons.
This was pre-Amazon when I was in grade school. No comic shops within driving distance of my home.
Mindblowing for the fact I had only seen the character in cartoons, the Keaton movie and Adam West. It felt like I was looking in on a strange new planet. I never got to read comics for another 15-ish years. Who here bought their first books at a drug store?