Exploding, Freezing Knife is Dark Knight-y
There’s a knife for sale on the internet (like everything) for almost $400. This knife will break your heart. The way it will break your heart is by freezing and shattering by shooting a jet of cold, compressed air into your body.
Designed originally for divers to fight sharks (seriously) the knife could be used on any soft, fleshy target. Like a watermelon (below). Or, if your Batman, a bad guy. If you are me, you could use it to open a can of beer.