20+ years ago it was .38 j-frame snub. These days it's a 9mm XDm 3.8 compact. That's more than twice the capacity and I went from around 860 FPS to 1,100+ with around the same bullet weight. I feel like I evolved some what! I would never carry less than a 9mm and I wouldn't recommend it for any one else. Well except for bad-guys. Bad-guys should always carry mouse-guns! Cheap crappy unreliable ones too!
Colt Mustang Pocketlite .380. Very accurate but hard to pickup the front sight in low light. As I get older my pants pockets get bigger so no imprint problems.