While it may not seem significant I have used my magnetized blade to both test a compass and be a compass , but to pick up small things, pins, and test for steel where so much is coated/painted another color. Magnetizing and demagnetizing is simple and do not change the metallurgy of the knife what so ever. Even some stainless is capable of magnetization and be a good indicator of the kind of metal it is. I often work on some things that use very small screws pins and clips ,and being able to pick them up with a knife tip is really cool .
As a Marine Electronics Tech in a previous life, I collected dead Magnetron Magnets to keep around the cabin for lots of uses. I have a collection of them that hold important Papers on the Fridge Door, as well as a couple out in the Tool Shed, that are quickly available if needed. They are good for testing Stainless Metals when determining Stainless Gun Metal...
That would IIRC be 400 series a ferritic form of stainless. The more usually found in consumer products is 300 series (par ex 17-4 ph), which is austenitic. The alloy is what makes the difference. Take a magnet with you when you go shopping. I don't see a lot of reason for a magnetic knife, but it is not difficult to do if you want to. I've magnetized several screw drivers, VERY handy.
I've always got a few magnets on me. Pocket screwdrivers, mini-magnets on key chains, and the clasp of my cigar cutter tether are all handy magnets. I don't intentionally magnetized blades, but find that most of mine are mildly magnetized just from use around other magnets on benches and tool trays. What I've found lately is that having lots of magnets in my pockets gets me locked out of my hotel, since they tend to erase the key card that opens the doors.
I own an pen size extendable magnet that I've used for picking up the stray nut or bolt that falls down into a cross-member while working on motors and other tight fit type things. Never thought about it, until this post, but I should probably add it to my EDC bag. So then I won't have to bend over to pick up all the loose change I find!
I have made large and micro mechanical fingers for getting things that are out of reach . You have to be smarter than the machinery . I keep al kind off magnets ,even made electromagnets to suit my needs . each have their particular value .
Canadian nickels were magnetic, when they contained nickel. They no longer do. However domestic F.R.N.'s are slightly magnetic, and show attraction to a strong magnet. Or a pretty gal's hand.