"Or not" by Dani Daortiz. Basically, you look away while a spectator cuts the deck wherever they want (or they don't. You don't care), then puts 3 cards (or more (or less (you don't care))) from the top (or the bottom, you don't care) to the bottom (or the top, you don't care), then cuts again (or not). Then, they take a card from the bottom (or the top, you don't care) and put it face up somewhere in the middle. They don't show the cards to anyone, but they can look at it and remember it, whatever they want. They do this 3 times, and put the deck back in the box. You then name the cards they took, and afterwards, you spread the cards out, and the only cards that are face up (or face down, whichever way you spread the cards), are the cards you just named.
You know, I feel the tone in which people say "Do that again!" is important. A certain tone implies they were PUZZLED and wanna catch you out, while another one implies that they liked it so much that they wanna experience it again.
This one is both at the same time.
On one hand, they think it's so impressive that "he must have done something" and they want to catch me this time, and on the other hand, they think it's really great that I can do it, and want to see more.
This one is especially great because you can do it as many times as you want, and they won't be able to catch you. The method is very subtle. Unless they know a lot about magic (sometimes even IF they know a lot about magic) they won't be able to catch you. At all.
And now I am just coming with my own personal experience here, and some logical thinking, so don't hang me up on this. But I think it's important to be confident and control your audience. If you don't have control over them and they start to disrespect you, this is when they will force you to do it again, and try to expose you.