Didn't techinically meet but I saw John Stamos once. It was when I went to California last summer as part of this big trip. We were on a tour of the Warner Brothers studio at the time. The tour was the Deluxe (read expensive) studio tour which included lunch at the "Commissary Fine Dining room", a restuarant within the studio. Anyway as we were leaving, it turns out Stamos was having lunch on the patio as well! We didn't get to do anything beyond looking at him, but it was still a cool experience.
Also we ran into the animals who play Digby and Pigby on Pushing Daisies!! And they were, of course, adorable!