Does it have to be a Ruger?
If so, my .480 SRH
If not, My Swedish M41B rifle- I have scores of rifles, some new, some over 100 years old, this one by far is my favorite and one of the most accurate!
Left: Swedish M94/17 carbine, Right M41B showing scope base
I really don't have a single firearm that I like more than the others. There are two that I have that will never be traded or sold because of sentimental value. They are my parent handguns that I inherited. These are the only two guns they owned.
1971 Colt Woodsman Series III (Dad's)
1971 Ruger Super Single Six (Mom's)
Dad liked semi-auto. Mom liked cowboy action. They both liked shooting the most affordable ammo. Then I was born in 1974, and their range visits stopped. That's why these handguns are in such excellent condition. I still have all the ammo my Dad never got to shoot.
Mine would be an employee-gun Redhawk, 7.5" from 1981. The Ruger employee had the Newport factory polish it out to a high gloss finish. Looks NIB with outer box, yellow box and papers. All mint as can be.
I'm in line, but in no hurry, to inherit an M1 carbine of 1944 vintage from my grandfather. It's a beautiful rifle & shoots like a dream. I only wish PA allowed semi-autos for hunting, as it would be perfect for that purpose. At any rate, it's easily the flagship of my family's collection.