None of them have been proven to actually generate anomalous thrust. The prior probability of such a thing working is so small that without dramatic evidence to

None of them have been proven to actually generate anomalous thrust. The prior probability of such a thing working is so small that without dramatic evidence to the contrary, they're all nearly indistinguishably equally unlikely. That said, "EM drive" prototypes have actually been built, as have Mach-effect thrusters, etc. None of them have convincingly been shown to work, mind you. This thing just exists on paper. It's not that hard to come up with a derivation on paper that's actually subtly wrong- much easier, sometimes, than actually finding where they went wrong.