Mine is a surprising one. An early '80s produced two pin Walther P1...provided the correct ammo is used. It's a little random on what it likes. Most 124 grain FMJ ammo? Yep. Most 115 grain ammo? Nope. 147s? won't even feed them. Cast or coated? "Who shot my target with buckshot?" Its especially sweet with the RMR 124 matchwinner or the mythical 124 WW-Olin milspec FMJ. AND they must be loaded with Autocomp, HS-6 or Unique. Anything faster and the groups spread. Local club had a "military pistol" bullseye style match, and this one used to really tick off the M1911 guys who spent a couple grand on their pistols at a time when the P1 was $250 out the door.
I have an Argentine P90 "Hi Power" that will give it a run for it's money. Never messed with the springs, I have to feed it warm 124gr ammo or it chokes. Other than needing snappy loads, this one shoots almost anything well, and the 124 Olin especially well. Interestingly neither pistol shoots 124 gr USA ammo especially well, which presumably has the same bullet. That bullet has been difficult to find as a component. Snapped some up earlier this winter and was quite happy about that.
These 2 are my most accurate. I have an FNS that I carry that eats anything and shoots it fairly well, but not the tight groups of the above 2. A witness-P came close, but I'd just begun working with it and a buddy offered a trade I couldn't pass up. Still shopping for another one of those! Wife's CZ P7 will shoot nicely, consistently, and pleasantly, but won't group with the P-1 or P90 given ammo that they like. I've also borrowed some various Sigs, CZs, Witnesses, 1911s, etc over the years, although most all were definitely superior combat handguns, none would shoot an itty bitty group like the P1 or P90.