Well, not enough people can appreciate the Ellis Ring, although that's a prop made for magic...
I don't think there's enough Pen or Cigarette tricks out there. Very portable objects, most people have on or the other now a days, and if they don't and you do, it's not as suspicious as bringing your own cards/coins.
Zippo lighters would be cool too, of course flourishes exist, but I wanna see a color change.
Hackey Sacks would be interesting! I was with some friends in a circle, kicking our hacks, and I ended up catching it and doing a color change I learned for coins and sponge balls, and then started the circle again. It got some laughs and a jaw drop, but I'd like to see something more impressive.
I just think easily portable things, or everyday apparel would be a good choice. Because when you tell somebody "I'm a magician" the first thought in their mind is card tricks, which is why some of the best tricks (in my opinion) are the ones that spectators don't expect.