Well, not really, because it didn't exist. But never let the facts get in the way of a good title, I say. But it does mean I have to explain what I mean.
The real V-weapons developed and used by Germany in the Second War War were the V-1 flying bomb and the V-2 ballistic missile, which are well known, and the V-3 multi-chamber cannon which is not. About ten thousand V-1s were launched towards London between June and October 1944; by the time their launch sites had been overrun by the Allied forces in France the longer-ranged V-2 was in operation, and was used to bombard London and south-east England until 27 March 1945. (The last V-1 strike on Britain was actually two days later; this was a long-range variant.) The V-3 was never fired at London but two smaller-scale versions were used against Luxembourg.
V-weapon is from the German Vergeltungswaffe: reprisal weapon. Their use against London was intended as a reprisal for the British bombing of German cities. This was something that had been threatened by Nazi propaganda many times. For example, after the start of Bomber Command's campaign against Berlin in November 1943, a spokesman for the German Foreign Ministry said:
Germany will now use her secret weapon as revenge for the R.A.F. raids.
On the one hand, Germany did not 'now use her secret weapon' on this occasion, nor on most of the others when similar threats were issued. On the other, it did have secret reprisal weapons in development and they were eventually used. The threats were not completely empty, but their constant repetition made them dubious.
One of the last of these threats emerged in late February 1945 and involved a so-called death ray (and an offensive use at that, not a defensive one as I have argued is more characteristic of the concept):
Latest German secret weapon is a V-bomb which, will release 'death-rays' sound waves of very high frequency which decompose living tissue — reports Stockholm correspondent of the British United Press.
Hundreds of these bombs, it is reported, are being built in underground factories.
Germans in Berlin and Stockholm are now mysteriously hinting that they will use these bombs if the Germans still retain their V-bases east of the Rhine.
Other reports suggested that 'the middle of March' had been set 'as the launching date for the new bomb'. It sounds like the idea was that the V-bomb would replace the high explosive warhead of the V-2, which was still in action.
Note that these death rays are actually sound waves, which is unusual as they tend to be described as some form of electromagnetic radiation. Apparently Germany did experiment with sonic weapons but it's hard to see how a sound bomb could work as described here. There were other possibilities for superscientific weapons: a rather good newspaper article about the sound bombs also discusses alpha rays, electron rays and dirty bombs in addition to electromagnetic death rays (including radio or 'Hertzian' waves), and notes rumours about German and Japanese research.
Oddly, this article was published in Australia, as were all of the press reports I've cited here. It's actually quite hard to find references to German death rays in the British press. Perhaps censorship is the reason, whether official or self (though many of the vaguer reprisal threats were published). Or maybe it's just that Australian newspapers weren't hit so hard by newsprint shortages (most British newspapers were mere shadows of their prewar selves by this time) so needed more filler material. Maybe it was simply thought too ridiculous. But the sound bomb death ray threat did make its way to the British people somehow, as the diary entry of London woman Ruby Thompson for 9 March 1945 attests:
Hitler promises to annihilate us with a Death Ray after March 15 He is supposed to have visited Berlin today, which we have bombed now for seventeen nights in succession. Oh, this war! Who will survive it!
Whether she or anyone else believed the death ray threat is hard to say. But with the V-2s still raining down it would have been hard to dismiss completely out of hand.