The airport is where I do most of my watch spotting. Lot of Pepsis, Datejusts, and Subs (two-tone especially). When I had the blue 39mm OP, the first flight I took after I received it, the guy in the seat next to me had the exact same one. I pointed it out and he didn't seem to have much interest in that fact.
Other than that, really have to go to a Redbar type event and hope that one of my buddies has picked up something cool to see anything out of the ordinary.
Earlier this year, I saw a guy peeling the protective stickers off his new steel sub in the security line at Maui airport.
Then on the flight to SEA I saw a couple gold steel datejusts and a blue dial gold steel sub.
A month or so ago the guy in front of me in security line at SeaTac had a Yachtmaster II that he just tossed in one of those bowls along with his wallet and phone.