RE: Guns anyone?
The thing is, you may think ammo cost doesn't matter because it's just one shot a year...but I think you should probably fire a box or two at least before going out. Really, that seems an absolute minimum. Make sure the scope hasn't been adjusted. Remind yourself of how shouldering feels, and get into the habit of taking a knee, using a sling to pull the rifle in, or take a seat. Remind your body how to do a smooth reload with the bolt or lever to get off a second shot. I've heard stories of people who fired one specific round, from one specific manufacturer...and then found a new box shot wildly different (this, of course can be mitigated by handloading).
Buying a rifle and expecting to only take one, or two, or three shots a year seems like the wrong approach. Both the rifle, and caliber, need to be something you like to shoot and feel comfortable with. For me this was the first year hunting since I was young, but I had a friend who formerly owned a gun store and had an arsenal. I couldn't shoot her Springfield bored to .300 Win Mag, but a .308 Savage 99 fit right. The ammo was cheap to practice with (all handloads in military brass), and the 165 grain hunting loads she whipped up had enough power to enter, punch through the spine, and exit the other side with a minimal hole. If anything they were a bit too powerful for a whitetail.
I don't think you can go wrong with any caliber that has been mentioned (and some that haven't been mentioned). Find a rifle that you love, and don't worry if it's the perfect caliber. Then shoot it until you feel comfortable.