Seven Keys to Baldpate
The magician presents a padlock and seven keys. A spectator is invited forward and proves that only one of the seven keys actually opens the lock. Once all the keys have been placed in a paper bag, six other spectators are invited forward and each of them selects a key from the paper bag. The magician then proceeds to successfully reveal which spectator has the one key that opens the lock.
The only props needed are an ordinary padlock, seven ordinary keys of which only one opens the lock and lastly and ordinary paper bag is needed. This is obtainable from any hardware store.
The teaching in this is excellent and there are no difficult moves to learn. The impact of this effect does, however, rely on the presentation. There is a couple of suggestion as to how you could present it, but this effect is a canvas on which you can paint your own personality and creativity.
In my opinion this is a really powerful effect, but I caution you to only perform this if you have a good story to go with it, else this effect will fail. There a lot of other versions out there, all of which uses either gimmicked locks or a change bag. This one really only uses ordinary props.
Seven Keys to Baldpate works well for a stand-up/parlour performance.