Those little attractive metal disks are a lifesaver in this hobby, allowing us to get more from our hobby dollar, or making delicate kits so much easier to move and store - I don't know how we used to get by without them. The case in point being this Leman Russ Demolisher I've been working on, which has fully magentised sponsons, sponson weapons, hull weapons, turret weapons and even turret basket cover! The best this being that this kit is so easy to magentise, which I suspect is the GW designers sticking it to the management, who would have us buy a new kit for each variation! I've gone down as far as magentising the arms of my Wych Cult so I can swap out special weapons - those are tiny magnets.
Here's a pic of the Russ, just so there's something to look at, it'll be joining my Lavuran Guard troops when I get it painted, right now I just wanted the box and sprues gone so I could tidy up my pile of kits! (Yes the multi-meltas are missing, those are on my desk, I found them after I took the photo, and yes the plow is not straight, it's not yet attached)