Well, you just asked an open-ended question and you're fixing to get so many answers as to boggle the mind as opinions abound.
Here's my opinion:
M1 Garand (.30-06)
1903A3 (.30-06)
Savage Model 11G (or GL if you're left-handed) (.223, .243, .308)
No.4Mk1 or No.4Mk2 British Enfield (.303British, most threads on these turn into discussions on handloading.)
Some sort of levergun. (Available in a variety of chamberings... .357, .44mag, .30-30Winchester, etc... can't go wrong with any of those.)
Mauser K98k (8x57mm Mauser)
Those are my centerfire recommendations, but do get a good .22LR rifle. Opinions abound on those too.