Interesting topic, but 10 seems to be quite a big number to make a sort in head But I'll try to do it - by chronology.
1. Seeing first "living" Atari at my cousin's and playing "Boulder Dash"
2. Having own 8-bit Atari on Christmas
3. Playing great single and especially two-player games which are often difficult to find these days on present platforms
4. Learning Atari Basic
5. Creating music with great Chaos Music Composer
6. Trying to create a Prince of Persia on XL/XE which I saw on 16-bit computers... in Basic language (!) (but I was able to create only two levels, and then I unexpectedly run out of memory)
7. And learning assembler with also great Quick Assembler kit, compared to 16-bit software in those times
8. Creating a cople of (paricularly graphic and desing) tools and game inspired by Flashback
9. Watching excellent demos from demo-scene
10. And crushing my Atari (so later was, and surprisingly still is - in another incarnation - "IBM" PC)
Anyway, it brought a lot of unforgettable memories.