A couple buddies and I flew out to LA to party with friends in 1996, a friend of ours 6'0 Blonde bombshell asked us if we wanted to go to a Birthday party with her. We show up really early at this tiny dive bar, and the bouncer asked her for the password. We get in and there was only a few people in there. We walk up to the bar and she says "Hey Leo, meet my friends from Iowa!" So I met Leo DiCaprio. He just finished with Titanic.
We asked whose birthday party it was and she said Jam Master Jay. The rest of the night was spent slowly walking around and mingling with the stars. I met Alanis Morrisette and probably could have scored. Mighty Mighty Bosstones were kind of who we spent the most time with. I was out in the back patio and at the time I looked just like Dave Navarro, sure as shit he was sitting about 10 feet from me with a bunch of models around him. They were pointing at me and laughing and he looked down and gave a nod. Beastie Boys were there as well but we couldn't get close enough to talk to them. I'll always regret that...
A few years later our friend moved to Chicago and worked at the Dragon Room which was owned by David Schwimmer. I spent a few nights partying with him over the next few months. It was actually cheaper for me to party in Chicago than Iowa City because she gave me a card that got me free entry and drinks to all the clubs.
Two years ago I was at the Four Seasons in Maui on St. Patricks Day. I was working out in the gym and there was only 3 other people in there. One was an old couple, the guy had long stringy gray hair and beard. I thought it was weird that they were staying there. There was another guy working out that I recognized as an actor but not sure who, anyway I got done lifting and grabbed what I thought was my cell phone off the shelf and headed back to the room. When I got to the room the phone started playing music, I realized I grabbed the wrong phone and went back to the gym.
I walked up to the old guy and asked if it was his. He looked at me and said "Nahhh man it isn't mine" I instantly recognized him as Kurt Russell. Then I looked down at the lady and it was Goldie Hawn. They were there for his birthday and over the next few days I saw them all the time. He was really cool and personable and was taking selfies with anyone that asked (I didn't).
I was home in Mason City and they were filming a movie there. I was in a bar shooting pool and the actors all came in and sat down, I was introduced to David Proval (Richie Aprile in The Sopranos) and Karen Black. When my friend told her I lived in San Francisco she grabbed me and took me to a little table. We talked for about 45 minutes. I could have hit it that night as she was all about me, but I couldn't bring myself to do it.
I've had drinks with Rob Schneider a couple times in San Francisco. We lived next door to a comedy club and he was always in there trying out new material. He graduated with a good friend of ours so we had a common friend. He was in Des Moines 6 years ago and my wife ran into him at Whole Foods and he took a photo holding our son, when she handed him over she said "Go to Daddy!" He got a good chuckle out of it.
I saw a ton of actors around SF when I lived there but didn't engage them in any way.
Edit: Forgot to say Ashton Kutcher. A buddy was dating a girl that graduated with him and we ran into him at the Sports Column this was in 1998 and he was just starting That 70's show. Nobody recognized him and he was all alone so he hung out with us for a few hours talking. Great dude.
TLDR: Leo DiCaprio, David Schwimmer, Kurt Russell, Karen Black, Ashton Kutcher.