Calvin and Hobbes, Tintin and Asterix have already been mentioned, and those were staples of my childhood - Asterix more than the others; I didn't quite appreciate Calvin and Hobbes properly until I grew up.
Yakari
Derib, the guy who drew/draws Yakari - and who is also responsible for the art of Buddy Longway, IIRC - is almost entirely responsible for influencing how I draw grass and stones and the outlines of distant trees. I don't draw them nearly as brilliantly at he does, but it's a work in progress!
Thorgal. I'm not sure I was supposed to read this back when I was oh, all of ten years old - it's definitely too violent and sexual to be age-appropriate - but it ran as a backup comic in Swedish issues of The Phantom (of which I also read a metric ton: The Phantom was never a big hit in the states, but he's a huge deal in Scandinavia).
Horse comics. I mentioned these earlier this week, but seriously, they were a big deal. I've read so, so many horse comics, and collected a metric ton. My inner horse-geek still misses reading them sometimes, but I think I gave them away; I kept them all in a giant cardboard box, because they were too many to fit on my bookshelves.