Originally Posted by Dr Nigel

Well, in his HH novels, he does point out (several times) that, if you can't maneouvre, all your enemy has to do is launch his missiles from a long way away (so that he can dodge anything you fire back) and give them plenty of time to reach very very high velocities relative to you. Then, the warhead is totally irrelevant (he calls this "kinetic strikes").

But, if memory serves, there was an even more OTT "unreal physics" tactic in E.E. "Doc" Smith's Lensman series: essentially, they neutralised the inertia of a whole planet, dragged it halfway across the galaxy, then switched off the machine that neutralised its inertia, so it resumed its original velocity (which was, of course, very large and in the opposite direction from the target planet).