I had a question about the size of magnets I use which is vitaly important. I bought my magnets from K&J magnetics. It took me three orders before I got the right size of magnet. The smallest I got on the top of the pile is 1/8" x 1/32" work great for figure arms. One magnet on the arm/weapon, and one in the model works great.
The next size up I use is 6mm x 2mm. I used these for magnetizing weapons on my warwalkers. I also used one on the weapon and one on the weapon mount. These are pretty powerful, and just a magnet and a nail or screw would have probably worked better. I have broken my warwalker putting these weapons on, you have to be pretty careful.
The largest size, I have yet to find a use for. These things would hold your nine-year old to the kitchen fridge. Getting two of these apart is rather hard. I will definatley use a nail or screw with the magnet for these larger ones. I was planning on using them for turrets or something.
I have loved using magnets on my models. Whenever I play a game, I can switch out the weapons. It does make painting take a little longer though.