Mine is barrel cleaning.
I wandered up the caliber range until you could tear off your shirt sleeve and shove that down the bore as it made life easier.
I detested cutting little squares or trying commercial ones made out of that putrid plasticy cotton substitute and fiddling with the damn things with endless loops, bore end pieces, brushes et al.
Smallest caliber (in the true sense) I have after rimfire's is .257 and that takes a lot of patience to to clean to the point it is over 25 years old and only fired a few hundred, mostly test loads. I then jump to 7mm where barely tolerable begins. My only muzzle loader is .54 and that's kinda nice. Used to have more .40 something caliber rifles than any other calibers in my rack.
If there is another, it is case trimming but I found a Lyman electric trimmer and that saved me.
What gets up your nose, but you have to do it?
