I grew up in Colorado and as my dad didn't hunt, I didn't start hunting until I was in college. Back then whitetail deer were scarce in Colorado, but I killed my first mule deer in 1965 hunting with my college roommate and using a .32 Win Special.
A couple of years later I got my first centerfire rifle, a .30-06 which was my main deer (and everything else) gun until about 1978 when I got a .257 Ackley. During that time, I also killed my best ever deer, a 30" non-typical muley in NW Colorado with a .45 caliber Kentucky percussion rifle that I built from a CVA kit, and I moved to Montana where I killed my first whitetail in 1975 with my .30-06.
Since I built my .257 Ackley just about all of the deer that I've killed were with that rifle, so I guess it would be my favorite deer rifle. I have however killed a few deer with my .22-250 and a few more with a .22 LR (which is legal in Montana).