I have a couple favorites, depending on what I'm hunting.
When I coyote hunt from a fixed position all day or varmint hunt from a portable shooting bench I like my old Savage Mod12 in 22-250. It has a shillen bbl and shoots true 1/4 MOA CTC groups. It is good to 800 yards in the right wind conditions. The bbl has a 1 in 8 twist so that I can shoot 95gr Berger VLD high BC bullets.
On varmint trips for ground hog and prarie dog, I also bring my TC pistol in .223 with a Mike Bellm barrel and a Leupold 2.5-8 VXIII. Its very good to 300 yards with handloads if the wind is under 20mph.
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For coyote hunting where I spot and stalk or call from different positions all day I use an AR15. I have a few .223 uppers but the bull carbine is my favorite for accuracy and fast handling in the woods. Its nothing special but the semi auto is very handy if you call in a double or even a triple of yotes.
For bigger game like deer, I like my .308s best. I don't have the right pic of this one but the brake has been replaced with a liberty suppressor (legal to hunt with in my state). Now it's only about as loud as a .22mag. It has a shillen bbl with a 1in9 twist and shoots high bc Berger VLD bullets which buck the wind much more effectively. Oh yeah, can't forget the Zeiss scope.
As cool as the bigger stuff is, I have to admit that I enjoy small game hunting the best. Its peaceful to be out without the stress and planning of a med/big game hunt. Also, since small game season is nearly four months long I can do it more often. I have changed favorites many times as far as my squirrel guns go. Lately I have been bringing a larger SLR camera so weight has had to be adjusted with my gun. I've only brought a .22 pistol on my hunts during the 09 fall small game season. It forced me to become a better pistol shot by trying to take only heads on squirrels out to 50 yards. The pistol I bring most often is a MKIII hunter, with all internals replaced with VQ parts and a Leupold 2.5-8 VXIII scope.