It's kind of funny because if you pull the pin...well, in this case the whole grenade...the tire will, well, not explode, but sort of implode as it loses air. Though I guess just removing the valve cap doesn't exactly release air unless you somehow manage to depress and lock down the valve stem pin too and...OK, fine, maybe it's not that funny. But grenade tire valve caps are rad because they're valve caps in the shape of grenades, and grenades connote cool things like Rambo and blowing shit up and circa 1991 blonde jokes, such as:
What do you do if a blonde throws a grenade at you?
Pull the pin and throw it back.
The aluminum and plastic pineapple grenade valve caps fit both auto and bike tires and come in bunch of bright and cheerful colors that the makers of real grenades should really consider incorporating into their otherwise gloomy bearers of destruction.