A Zamboni has a "conditioner" at the rear that contains a sharp horizontal blade that shaves the ice as the machine runs across the ice. The blade is a bit like a very wide wood-plane. It is sharp and controlled to be a little below the current surface of ice. The shavings are moved to a waste tank using an internal horizontal auger and vertical auger.

You usually couldn't get near enough to the blade to have a close enough shave for it to harm you. However I'm guessing a Zamboni could hurt you in other ways.

Disclaimer: I only skimmed the details . . . I'm sure applying the right amount of intelligence could discover harmful means.