I own and use several rifles chambered in what you might call "less then mainstream" cartridges.
Some are probably more popular in Europe and maybe Oz, but here they are a bit uncommon.

From small to large I have;
1 222 Remington
1 257 Roberts
1 6.5X54 M/S
2 300 Savages
1 303 British
1 300H&H
1 8X57
1 35 Remington
1 358 Winchester
1 9X57
2 9.3X57s
1 9.3X74R
1 404 Jeffery

I also own several rifles in popular cartridges too. So I am not bent on one side or the other.
I have:
223s
25-06
6.8SPCs
270s
30-30
308s
30-06s
7.62X39
9.3X62
375H&H

I like them all.