Somebody told me about a effect called "Zap", which is supposed to be a hypnotic technique. Sounds like a Derren Brown kind of effect... any mentalist here heard of this?

Is it Zap by Hon Wong? If it is, I do not think it is very "Derren Brown" since Zap is Instant Trance thing. Plus, it is kinda rough and violent :P (the trailer shows, him pulling someone to the floor with a command)

Hmm, the basic item is the instant trace hypnosis technique.

But they did is actually providing a shock to the brain, causing temporary concussion, its like when you are walking and your joint accidently hit a corner and the shock wave cause you to suddenly fall down with weaken leg etc.

The actually instant hypnosis is actually very complicated, going into choosing the correct audience, and respecting the audience that you did the hypnosis to. And not just randomly going to people and make them sleep. Thats so mean.