I guess I'll chime in with mine here...there's a few of them:
The day we adopted Tamlyn
The day I almost fell out of a tree onto Slash from Guns N Roses and got to hang out with him afterwards
The day I discovered I wanted to make my living with my camera
A Chaka Khan concert where I won the bass guitar used in the show signed by Chaka herself.....then got to go backstage and meet her.
The day my fiance asked me to marry him
The day I adopted Cissy (actually a bittersweet day....but that's another story for another day)
The day I got my acceptance letter from Art Center
and finally, the day I quit my crappy job to start attending Art Center
There's also every day I have with Tamlyn and Cissy, watching them grow. But that goes without saying.