Best: The only really good one I can think of right now is beating my Uncle in Street Fighter 2 for the first time ever. I spent most of my childhood trying, and it took me until I was 10 years old to beat him even once. Now I beat him pretty much every game, but it just isn't the same. I'll always remember that one game: I was Ken and he was Guile (his best character, no less), and he was spamming Sonic Booms. I managed to back him into a wall, and managed to make my way up to him using a mix of blocking, hadokens, and jumps. When I finally managed to kick him in the head, we got into a fistfight OF EPIC PROPORTIONS (probably my memory blowing things out of proportion here), finally ended by a point-blank Hadoken by me.
Now that I've taken my rant of an overly exaggerated trip down memory lane, it's time to move on.
Worst: When Strike One closed down… Strike One was an awesome place in my town, an arcade/indoor playground where you paid for admission and then all of the games were free. What's more, there were never lines anywhere. It was heaven! My friend and I must have beaten Altered Beast 10 times over the years of birthday parties I had there. When it closed down, I was heartbroken.