Funnily enough, what I remember best are always the moments of frustration and/or heartbreak, but in terms of favorite moments, I guess two come to mind.
Firstly, playing for my school XI, I came in at number 10, and was accompanied at the wicket by our number 11 who was a six-foot plus beanpole and couldn't bat for peanuts. We had five overs and obviously only one wicket in hand to get 30-odd runs. I hit two fours and two sixes, and after the change of ends he was clean bowled. Doesn't sound that impressive, but the reason it was so great for me was that I'd been a fairly impotent medium pacer up to that point who was rarely given a bowl, and I'd been a very timid tailender with the bat, who opened the face of the bat far too often and didn't hit straight. That innings (for which I got a lot of praise and pats on the back) was the first time I realised I might actually be useful with the bat in my hand, though I'd always wanted to be a bowler.
After that was probably the three premierships I captained in junior comp squash, as my team moved up the grades from E res to B res (we ended up a pretty fair outfit, and we absolutely sucked when we started). Including my defeating of a massive guy we called the Thundercrack (because of the sound his hand made when he hit the wall with it after making a mistake - it also seemed to make the gallery above shake) to whom I'd lost in our last encounter.