The Human Sentry Buster is what you get when you fuse a Demoman and a normal sentry buster together. He is neither man or machine: while organic, he bends the laws of physics and biology simply by existing, and can defecate Ullapool Cabers. Since he self-destructs, his self is destructed when he explodes, and he dies instantly upon "detonating", since his brain is made entirely out of crossed wires and potassium chlorate. Unlike any other sentry buster, this one has a personality and can talk.
No other major differences between him and a normal sentry buster exist.