I have quite a few things still from my first trip in 1974:
Two souvenier books, one is the D-shaped one with the cutout about building the park and one is a general one about the park as it was then.
An old ticket book and information guide: GAF was the film sponsor then!
Slides of course as my dad wasn't with us and he was the photographer of the family

View master reels of Adventureland, Liberty Square, Frontierland and Fantasyland.
A Mickey mouse charm, and I think I've still got one of the Mickey earrings somewhere.
I know I also bought a floppy sun hat with Mickey on it but that's been lost. And recently I found part of Big Al. He was in a pop out book to make your own 3D country bears, as someone said, they were huge back then!
After that I didn't get to go back for a looooong time, but when I did, in '97 I got a TOT T-shirt and it's still good! I also got the 25 year anniversary Litho and stick on badge. Don't know where the Litho is but I've still got the badge!