The easiest to take on and off are the ones made to mount up to a rail. Obviously that isn't an option with a Ruger Scout or Savage .22.
If you are going to spend the money, a Harris is your best bet. They are durable and lightweight. They mount to the the sling swivel stud.
Herman Cain '12
Squished bugs on a windshield is proof the slow/heavy bullet theory works.