Definitly the Ruger 10/22. Anyone who tells you they are junk doesn't know jack about them. They cant be beat in price and reliability. And as it was said, you can customize them to your heart's desire. There is no end to the possibilities. Theres even a kit to put 2 of them together and make a dual-barrell gattling gun!
Duct tape and some string?
I'd go for a 10/22 as well. Don't have one, but I'd get one if I was picking up another 22.