If someone handed me a coin and told me to do a trick then I would refuse. But if you want to impress them with a coin effect then using a Quantum Bender to bend the coin can't be beat.
That's great and all but the quantum bender insn't something you'd have on you plus it's like a gagillion bucks.
And if someone handed me a coin out of the blue and asked me to do magic I'd say no and put my hands back in my pockets only after I did a really good non shalant (sp) false transfer to give it back to them. So it would go like hey do a trick with this coin * hands come out of pockets, right hand accepts the coin, false transfer into the left hand, right hand goes back into the pocket* "no" * left hand gives them back the coin that vanishes the instant it hits their hand, left hand goes back into pocket and you continued talking about whatever it was you were talking about paying no attention to the fact that you just made a coin vanish which should make it very strong and real for them*
I happen to keep my hands in my pockets often so this works for me. If I don't have my hands in my pockets I put them in and pretend like I didn't hear them or are ignoring them for a second then put my hands in my pockets and after a second I turn to them and say "what" and they go "do a trick with this coin" and then you do it.