For me it's definitely the 222 Rem. My mates and I all have them in a variety of guns. Krico 600 (mine), Sako 85 Hunter, Tikka T3, Winchester model 70. With a good soft point or hollow point 50 grain bullet they are dynamite on foxes. I use Norma solids on hares and rabbits as they don't blow them to bits. I have also collected about 150 rounds of brass in 222 Rimmed including a box of factory ammo made by the Super Cartridge Company. One day I would like to have an Under and Over combination gun in 16 Gauge over 222 Rimmed. Would be very handy for some of the terrain that I hunt foxes in.

I also use a 22LR with Winchester 42 Grain Powerpoints. They are exceptionally good killers of foxes out to 100 yards. The heavy bullet really hits hard. I have never needed more than one bullet on foxes and feral cats.

I have also used a 22-250 quite a lot, it was in a Sako Model 75. Very accurate and extremely deadly on foxes. I was using Speer 52 grain Hollow Points and that combination is not ideal for collecting pelts. On the other hand, if you want to blow a hole big enough to fit your head into then that combo is great. The 22-250 kills out of all proportion to the size of the cartridge and projectile. Very nasty.