The probably most exotic cartridge I reload and shoot is the 7.5x55 Swiss, a very neat round, it looks like the love child of a .30-06 and a .308, its the perfect in-between. Fortunately .308 bullets can be used with no overpressure and very good accuracy from my straight pull bolt action K11. It loves flat base bullets.

Then I also have the .44-40, which is such a classic. Such a gentle and extremely accurate round, 200 grains at 1380 fps with nearly no recoil. I'm sure if my Uberti Lever action was scoped it would shoot MOA with it. At 50yds with 200 grain lead round nose it shoots 5 rounds all touching and at 100 it still is less than 3 inches with buckhorn sights!

The most exotic I ever had was the 7,65x53 argentine in an 1893 Argentine Mauser. It was like a 7,62x51 that uses .311 bullets instead .308. I remember I used .308 load data for my first reloads.
Sweet shooter, but cases and dies were hard to find