I'm in good company, my 1911 is the best natural out of the holster gun I have for handgun, next to my Model 29. Its such a natural fit in the hand, so graceful and balanced, it flows and fits right. My 29-2 is a masterpiece, its My Gun at the end of the day, but if that 1911 GI just isn't just the perfect fit whenever you get back to it.
For long guns my PTR91 is the most natural up to the shoulder in combat rifles. The old 20 gauge Mossberg 500 youth from my squirrel hunting days is something that goes so naturally its like the gap between many years of use never happened. For bench shooting, my CZ 550 is always a nice trigger to return to, always exactly where you remembered it. I can "drop it off" and return to training with it at any time and not lose anything.
Interesting question as I ramble free association style. Trigger confusion is a real thing and can really screw up a man, along with the usual problems of getting rusty from lack of shooting. Certain guns you can quit shooting for extended periods and pick right back up, others are a humiliating reintroduction to an old friend. Grab an old accurate gun you used to be really in sync with but quit shooting for a while and you can be astounded how inaccurate it has become (can't be you of course) from sitting idle. I used to do shoots on the property here doing 5 round strings from three different handguns in constant rotation, all three I can shoot well, and it can be surprising how such rapid change up can throw you off.