I too am intrigued by less common rounds, and tinkering with loads that haven't been beaten to death in more common rounds (like the 180 woodleigh in 270 Winchester…developed a load literally because I wasn't aware of much data out there and wanted to go into that uncharted territory and create some to share with others
)
My .243, 270, and .300 are very common (though I don't know anyone else whose worked up a 120 gain Barnes to 4000 fps in a .300 winny)
My 257 weatherby isn't common but I know more than one person in my life who also has one. Not many have tried the 75 hammer hunter in it though, so that's my something new. In progress.
My 8mm mauser is no doubt common in some places but not where I live. I actually don't know anyone personally who has one. Got rid of my .308 cuz it was so boring. No real need for a .30-06…this 8mm is the same thing ballistically but it's cool
My most uncommon and favourite Rifle and cartridge of my collection right now is a .358 Norma. Definitely not everyone and their dog has one, in the same company as that 8mm rem mag.