With the proliferation of accurate bolt rifles in 6.5 Grendel and light weight bullet for varmints would be great. Something like a Varamageddon at about 75gr for colony varmints would be great.
For me it really depends on where and what I'm hunting. I mainly hunt coyotes, but do it a lot in various states.
For my combo guns(rifle/shotgun) 12ga/5.6x50R Mag and 12ga/22 Sav. Highpower(5.6x52R the Leupold 1-4x20mm for the ability to mount them low and the huge FOV for close in moving...