I'll toss my varmint killers in the ring:
.22 Cal Air rifle
.223/5.56 --- 5 different AR's
.220 Swift
6mm ARC
.243 Win.
6.5 Grendel (my wolf rifle)
6.5 PRC, and for really tough larger varmints:
30-378 Bee slingin a 124g Hammer Hunter @ about MACH 78.3
Well, since everyone is posting groups here are a couple. Both of these are from factory rifles!
My Weatherby Super Varmint Master in .243 Win. I ABSOTULEY love this rifle!!! Not too bad for factory ammo and rifle.
She's a killer too!!
Next group is from my VERY first (purchased by me) rifle. A tang safety Ruger M77v in .220 swift. She is a safe queen now but if I had a dollar for every squirrel, crow, yote, or marmot, hell I'd go down to the Ford dealer and order me a new Tremor Super Duty!!! This group is .188 and it's 3 @ 100
Here is another AR yote slayer, my wolf rifle in 6.5 Grendel, I'll have to look for group photos but she'll shoot in the high .3's all day!
Last one, Marmot getter, this is a .223 Wylde chambered Lothar Walther 20" bbl. Shoots lights out!!!