I was riding my Brompton folding bike home today, when a sudden thunderstorm forced me under an awning in Chinatown. As I was checking my mail on my phone, I heard some tapping behind me.
This guy in the closed up shop I was standing in front of was gesturing at my bike and gave me a thumbs up. I waved back and smiled. He went into the back of his shop and came out with his own folded up Brompton.
A few minutes later he had walked outside and we had a really nice chat about our bikes, what we like about them, who our mechanic is (David at B-fold), and other bike geek stuff.
This happens to me all the time on my Brompton. I think it's a specialized enough bike that it gets noticed by a lot of people, sparks their curiousity, and makes them want to interact with the owner. Often they want to know how it is to ride, how much it costs, and how much trouble it is to fold up.
I don't think there is anything else I own that creates such openings for random stranger conversation as my Brompton.
Back when I got my first gen iPhone, it would literally stop people in their tracks. They would walk up to me and ask "is that really a…?" And then they'd want to play with it.
Some books have caused me to start chatting with people on the subway, particularly if its one of my favorites.
When my then girlfriend would pull out her knitting needles on the subway, invariably the person sitting next to her would start talking to her about it. "What are you knitting?" "Where did you learn?" "You remind me of my grandma."
And of course there's the old guy tactic of walking around with a cute dog to get girls to come up to them.
What other things can you carry with you that cause strangers to start talking to you?