I picked up a Ruger 10/22 at walmart for around $200 (I've seen them on sale at $175), and it came with a bolt on picatinny rail and predrilled mounting holes. There are many aftermarket stock options, to include a 10/22 Tommy Gun kit for the Thompson enthusiast, but I went with a TAPCO tactical stock for around $89. I threw on a cheap red dot sight and a high quality bipod that I had from my days in the Marine Corps, and I've been using the thing to take head shots on moving squirrels (no wasted shoulder meat that way).
My favorites about the Ruger 10/22 is that there is such a large selection of aftermarket accessories, that often don't require any gunsmithing. Retrieving the weapon from the stock is a matter of removing one bolt if I remember correctly. They also have a nice selection of magazines. In addition to the nine round box magazine, ruger now makes a 25 round bannana clip magazine, and I have seen some neat looking 50 round drums. Aftermarket mags can be good, but I would reccomend only buying the magazines with steel feed lips.
- Count your blessings by the magazine full.