.30 Mauser (for a Broomhandle), 7.62 Nagant (for a Nagant), 7.62x25 for Tokarev's and a CZ-52), 32 S&W (for several topbreaks) 38 S&W (for topbreaks as well as some 1970's vintage J frames, and a 1938 vintage M&P, (9 Largo, for an Astra and a Star), .32-20 (rifles and revolvers from an old M&P to a Browning 53) .38-40 ( for a Win. 92, Colt new Service and a Ruger Blackhawk), .44-40 (for a Win. 92).
8mm Lebel (for a Lebel rifle) 8mm Kroptaschek (for an 1886 Portugese service rifle), 8X50 R and 8x56R (for the Steyr model 95's), 11 mm Danish (Rolling Block), .43 Spanish ( Rolling Block), 7.5 French (MAS 36), 7.35 Carcano (for two ex-Finn Short Rifles), 6.5 Carcano (several carbines and rifles), 6.5x53R ( Dutch carbine made by Steyr), 8x52R (Siamese Mauser), .25 Rem, 30 Rem. 32 Rem ( For Rem. Model 8's), 7.65 Arg. ( Belgian, Argentine and Peruvian Mausers), 6.5 Jap and 7.7 Jap. (Arisaka's).
I am sure there are others. I didn't include stuff like 8x57, 7.62x54R, and some others because its not really odd anymore. Not like it once was.
My first experience with weird calibers was 7.62x39 for an SKS a relative picked up in Vietnam. There was no ammo available commercially so I pulled the bullets from 7.35 Carcano Italian military ammo and formed the cases by moving the shoulder back, upsizing the mouth of the case and modifying the rim. Back in the early 1970's there was a glut of 7.35 ammo dated 1938 and 1939 so it seemed easy enough. Of course since the brass was berdan primed and and an odd sized berdan primer to boot, it was only good for one firing and in those days I had to use what I had. Those 7.35 bullets were used years later to load ammo for 7.35 that I formed from 6.5 MS or 6.5 Carcano brass. I still have some of those pulled bullets but I mostly use cast in the 7.35's just for plinking, but I have also swaged down .308 and .310 SP's for hunting.