You think of water and fire as opposites, but it doesn't have to be that way. If you're clever enough about it, they'll get along together just fine. And there's just always something so paradoxically cool about starting a fire with H2O.
As the King of Random shows off here, there are a couple of different ways to go about setting a blaze with tap water and household goods, but it's not quite five. Really, the trick is just to find a way to focus light, and there's a bunch of slightly different ways to go about it. Alternatively you could find some sodium for real fun, but it's probably easiest to just find a book of matches. [The King of Random]