I've discovered the joys of magnetizing as part of modeling my army. Interchangeable wargear options are a godsend. So far I've magnetized a new Captain, and some of the models I just picked up for our upcoming Planetstrike Campaign: an Ironclad Dreadnought and a Land Speeder. I'm going to need to grab some more soon.
The magnets used are 1/8"x1/16" magnets purchased off EBay specifically marketed towards Warhammer players by the sellers. Unsure of the retail brand name.