How old is your nephew? Preteens that have zero firearm knowledge are typically best with a single shot bolt or break open, there are many good brand options for all of these type of rimfire rifles starting with the Cricket. With teenagers and semi-autos in mind it's hard to beat the 10/22 ... but ... I find the Winchester Wildcat is excellent as well, at a much lower price tag, it can use 10/22 mags, AND has the added benefit of bolt hold open on the last round fired. Sights are important, too. There are advantages to learning the use of iron sights from the get-go, but scopes will be far more accurate and help stimulate firearm interest.