Don't you just hate weapons that are stuck in place? So do I, so I wanted something different for my Warhound. What I decided on was use using 4 magnets and 1 ping pong ball for each arm. I cut the ball in half, and sealed 2 magnets inside and glued it to the arm. Now these 2 magnets inside are free, meaning they are not glued in place, you can hear them rattle around in the ball.
The 2nd two magnets are glued on the outside part of the other half of the ball, and then mounted under the shoulder on the Warhound. Outside is important because you want the two halves of the ball to be able to rotate inside of each other.