Three other possible rounds that no one has mentioned are the .17 Mach II, .17 HMR, and .22 rimfire Mag. The 17's are fairly "new", but I've noticed a pretty good selection of both rifles and handguns chambered for them in my gun books. I don't have the ballistic charts handy, but did recently compare the 17's, depending on your situation, any of them should work.
A friend of mine longlines for fox around the MD, WV and VA intersection, the only firearm he carries is a .22 Mag rifle. He totes it for the incidental coyote, and feral animals. Last time we talked about yotes, he told me that he'd stop 30 or 40 yards from the animal, and shoot it in the heart/lung area.