Anamorphosis and forced perspective mess with your mind more than any computer-generated effect
Anamorphosis is the technique of using perspective, or a deliberately geometrically distorted projection of an image to create the impression that things are not as they seem. It's a way to trick the powerful interpretive mechanisms in our brain into seeing the world differently.
Here's a great example, used by Honda to creative effect. It also uses Forced Perspective - where real objects are deliberately resized to trick is into thinking that other objects (people for example) are either bigger or smaller than they really are.
This will really mess with your mind.
And the best thing? There's no need for CGI.
Video after the break