I regret not being able to go to any of the Fountain Valley Fry's midnight releases that were hosted by the Blizzard dev teams. I wasn't even in high school yet when those were still being held. In hindsight, I think my mom would have been willing to take me to one if I had asked. It was a ten minute drive from home.
I was really sad when that Fry's closed down. Nearly all of my PC gaming purchases came from there and the ACP Swapmeet up until 2006 or so, when I switched to Steam, so it felt like losing a part of my childhood. I haven't visited the location in a while, but I'm assuming it is still empty and fenced off.
The first dinner I ever ate after arriving in SF was at their original HQ's cafe/restaurant, thanks to some friends who worked there. It was so good! I regret not having gone as a guest more often.