Well for true varmints, I would probably go with my old MDL 70 in 243. Loaded with the 85 or 95 gr BT it rocks. However, I have taken more critters of the vermin type using my 25-06 than anything else I have. From 20yds to 400+ it served me well through the years I had posesssion of it. Now my daughter has it and I hope it serves her as well.
Of course varmints around our stomping grounds are a bit different than most of yours. As such I would have to say that other than the 25, my Ruger Compact in .308 has picked up where the 25 left off. I have taken several coyotes in close with it as well as several fair sized hogs out further than I really imagined it would drop them. However, when they present a target, I will send something their way. Here are a few that have fallen to the .308,
A quick 45 minute hunt down by the gravel pit,
First long range hog with the 308, just over 280 yds. in the last minutes of light,
A very mangy yote, hey remingtonman_25_06, ya think those 17 caliber fellows would have wanted this one's pelt as well?