Hall-effect thrusters throw ions at 15 to 30 Km/s, or 0.0001c. There is one other thruster that doesn't need a tank of reaction mass: a photon rocket-- moving

Hall-effect thrusters throw ions at 15 to 30 Km/s, or 0.0001c. There is one other thruster that doesn't need a tank of reaction mass: a photon rocket-- moving yourself around only using radiation pressure. Exhaust speed really is c, but generated thrust is tiny, since photons are pretty light. The resonant cavity thruster is more interesting than a photon rocket, since its thrust is much higher.