The most popular modification is probably the installation of a heavy barrel and larger stock, often a thumbhole style. Mostly competition shooters originally made this modification, but a lot of hunters make these changes because of the outstanding accuracy resulting from the heavy barrels. Kits are available to make the 10/22 look like a German MG42 WWII era machine gun, M-1 Carbine, or even a Garand. You can dress it up to mimic an AR-15 or just bolt on a bunch of tactical bling to bring the gun in line with current trends. There seems to be no limit: from stocks and barrels to triggers and98 magazines, the shooting world is filled with goodies for the 10/22. Which is fine, because the shooting world is also filled with Ruger 10/22 rifles, so it all balances out quite nicely.