The ability to say "no" in a variety of ways and contexts is an essential part of being socio-cognitively human. Through a variety of examples, we show that, despite ominous portrayals in science fiction, AI agents with human-inspired noncompliance abilities have many potential benefits. Rebel agents are intelligent agents that can oppose goals or plans assigned to them, or the general attitudes or behavior of other agents. They can serve purposes such as ethics, safety, and task execution correctness, and provide or support diverse points of view. We present a framework to help categorize and design rebel agents, discuss their social and ethical implications, and assess their potential benefits and the risks they may pose.