A Weatherby Mark XXII semi-automatic, either the Italian or Japanese made editions. At least I look good carrying it, even if I can't shoot worth a dang.
Very close second -- a modestly customized Ruger 10/22. I like the ones made by Clark's with the mid-diameter barrel mounted on a sporter stock. Little tiny groups and light enough to walk the field with.
I think Volquartsen used to make something called the Firefly built on the 10/22 pattern, which was made to shoot .22 Shorts. Never seen one in the flesh, but that little rifle has always appealed to me.
Bullseye
P.S.: Somehow, I missed that this was supposed to be a recommendation for a young one. I definitely concur with the single-shot school of thought on this. Of course, if the rifle is being shot under supervision, the magazines on the semis can be loaded one round at a time.