A.H. Fox immediately comes to mind. The old Philadelphia ones especially higher grade came with 4 or 5 different barrel weight. The ones with lightest barrel profile are truly "toyish". When I examined "C-grade" 16 I had to rub my eyes and when I looked back it wasn't 20ga as I thought but still a 16ga, amazing. If you want something else I suggest 12-20 concept pioneered by an English company and propagated by some Basque makers.