Hitchhiker's Guide to the Galaxy - The Restaurant at the End of the Universe

Marvin stood at the end of the bridge corridor. He was not in fact a particularly small robot. His silver body gleamed in the dusty sunbeams and shook with the continual barrage which the building was still undergoing.
He did, however, look pitifully small as the gigantic black tank rolled to a halt in front of him. The tank examined him with a probe. The probe withdrew.

Marvin stood there.

``Out of my way little robot,'' growled the tank.

``I'm afraid,'' said Marvin, ``that I've been left here to stop you.''

The probe extended again for a quick recheck. It withdrew again.

``You? Stop me?'' roared the tank. ``Go on!''

``No, really I have,'' said Marvin simply.

``What are you armed with?'' roared the tank in disbelief.

``Guess,'' said Marvin.

The tank's engines rumbled, its gears ground. Molecule-sized electronic relays deep in its micro-brain flipped backwards and forwards in consternation.

``Guess?'' said the tank.