I believe I heard that magnets lose their magnetism after shock, or being hit with something.

I'm a sucker for cool magnets. I would probably get something like this. I like the idea of making them rubbery.

There's been magnetic darts before. (I have some in my room) just saying that they're for a 'Fridge' might get it some people to buy it, but I think at least one person has took a magnetic dart set and put it on their "cooling device"

Need to make sure the magnets won't fall off when the fridge door is opened and closed. I think this might be a problem if the dart magnets are the same length as a real dart. A solution might be to make the tail a little shorter.

Like fridge magnets. They are unfortunately not compatible with stainless steel fridges(stainless steel not magnetic). If you go this way, Neodymium magnets http://www.thinkgeek.com/gadgets/770f/ should do the trick. I would not make a plate at the fridge contact - it seems excessive.

I misunderstood. It's a fridge magnet. Pro: Draws the eye, like an arrow. Con: Sticks out.

Cool idea... two thoughts. One, add a simple timer to it, added value and cheap upgrade.
2) along the lines of "not wanting to run into a metal dart sticking out of my fridge", add a hinge between the hand grip and the shaft so that you can bend the darts out of the way if you choose.

Include a metal target board for stainless steel refrigerators. There is a material that sticks great to stainless steel. I've used it. http://www.mayfairlane.com/index.html

make a nerf gun like device and there will be awesome

Marc, i think J Oster has something going on there!!
It makes this product have more value and become the novel that you want it to be like the Jägermeister(??) thing.

Cheers