Looking at Battle of Tsushima, 1905, something that struck me was
And finally, by 27 May 1905, Admiral Tōgō and his men had two battleship fleet actions under their belts, which amounted to over four hours of combat experience in battleship-to-battleship combat at Port Arthur and the Yellow Sea.
which kinda implied that, in 1905, they were pretty much veterans in terms of having commanded new-style battleships (armored, steel, steam powered, using mostly large guns) in combat.
Battleships, through the Dreadnoughts, then became the backbone of Western navies.
Yet, by 1944/45, battleships were pretty much obsolete, besides being used for shore bombardment. From Tsushima/Dreadnoughts, that was a major weapon system that went from dominance to obsolescence in less than 40 years.
What other weapon systems have come and gone very quickly?
has to be a major/dominant/war-winning weapon. Zeppelins were never that important, for example, so the fact they only lasted for a few years doesn't count.
Technology turnover is much quicker nowadays, so a similar development in ancient times or the Middle Ages could count on a longer lifespan.
"Weapons systems" is loosely defined. The Phalanx was fairly dominant for some time, but eventually opponents learned to flank it. That would count, except that it lasted for a while. And, no, pikemen in the Middle Ages wouldn't count as a continuation of the Phalanx - phalanxes were a specialized infantry-on-infantry formation, while pikemen were meant to stop cavalry.
Other candidates - except that their lifetimes, while limited to a small slice of the historical record, was not in fact all that short - might be crossbows or war chariots. After a while, they pretty much disappeared from large scale use in any given theater.
- it has to be recognizably distinct from its predessor
Japanese, Chinese or other non-Western weapons for which there was both large scale use and a clear historical record are fine.
Edit: in response to lack of clarity in my question so far:
I really meant a weapon that disappeared on its own because it didn't work anymore, but it had, at some point. Essentially a counter-weapon/tactic had been found to it and, except for militaries too incompetent to realize it, it won't be used anymore. Polish cavalry charging the Nazis in 39 is already behind on that clock, except for the bravery factor which is sadly timeless.
It is particularly distinct from what related weapon/systems recently preceded/succeeded it. Sure, V1s were very much a flash in the pan in 44/45, but cruise missiles are now very much staple technology - V1s are essentially unsuccessful recent predecessors to modern cruise missiles.