Ruger 10/22. Period.
There are more stocks, barrels, actions and parts for that rifle than just about any other and there's not a gunsmith worth their salt that hasn't "massaged" a slew of them while practicing his or her trade.
Customization on that rifle comes fairly cheap and reliability is beyond compare. I've seen some that are more works of art than "gun", so it's the Honda Civic of gun modding (in a good way).
Google for the gun and you should get pages of custom 10/22s for your viewing pleasure.
