The Al Baker effect is a good one that is easy to do an completely impromptu but still has the
"feel" of real mentalism.
Things are written down before choices and actions are made,and
eventhough the method is easy to execute, it is not concievable to "regular" intellects because how
did you know their number and because as mentioned earlier it is written down before they make their
choice.
You can borrow everything you need as well. No sleigths either but there is a
very, very simple "move" that reqires a second or two of misdirection. Luckily since you are about
to predict the future you just tell them to look into your eyes or something along those lines and
do it while they are looking at you...They won`t know the better. You can potentially utilize pinky
break to mask it even more
I`d say that one is a good reason to get this lesson.
Other effects are good too, but some are a bit long (for my taste anyway...)