This is tough because I have needed, or wanted, different things from different guns at different times. My all time favorite rifle is my Dad's .303 with a Charles Daily 4x16x40 scope:
He gave it to me after he modernized and got a new Ruger in .270. He still says that's when he stopped killing deer and I started. Prior to that I had missed or wounded and couldn't find a lot of deer. After that I never lost or missed another deer and I've lost count of all the deer that old rifle had put in the freezer. I've dropped deer in their tracks at 300 yards with this rifle.
Sadly it's showing it's age and I finally modernized as well. My current favorite rifle is this Rem M700 5R with an M24 milspec barrel in .308:
It's got a Burris 4.5x14x42 Fullfield E1, and it's my current go to deer rifle but I still have different lighter rifles for long hikes and so on because I don't like carrying this one all day! It's tough picking my favorite rifle because years ago I didn't have the choices I have now. I love the Rem 5R but I can pick lighter rifles if need be. Years ago I had my .303 and that was it. That .303 had to do everything, and it did. For that reason it's still my sentimental favorite, but nothing shoots close to the accuracy I get from the 5R.
I'm also a fan of big bullets and shoot 180gr Gameking hand loads in both.