COTW has probably the most extensive list of shotgun and smooth bores. Some true gauges missing from your list are 11 gauge, 15 gauge, 18 gauge and 32 gauge.

11 gauge - two double barreled guns and about 200 shells were made in the 1890's.

15 gauge - only listed for one year in the Winchester 1877 catalogue with brass shells. A rarity only found in the best collections.

18 gauge - European gauge made for custom shotguns. UMC made some for an experimental Browning shotgun sometimes with a 20 gauge headstamp. European pin fire versions also existed.

32 gauge - Made well into the 1930's with other loading batches made in later years. Fiocchi making shells in recent years.