Water - we drink it, bathe in it, and use it to make everything from hamburgers to t-shirts. We just manage not to think about it much... for now. Put on your thinking cap for this one: today we're fighting wars for a finite resource: oil. In years to come, we may well be fighting wars for another finite resource: fresh water. Think about giving one up - which one can you absolutely not do without? Right. What does that imply for the scale and severity of the potential war fought for the resource? It seems to me that the war would be in direct proportion to the urgency and necessity of the resource in question. I'm far from the first to raise the issue - The Great Lakes Water Wars (2007) is a topical book I have heard a lot of good things about. Hydropolitics may not be the sexiest topic, but it's worthwhile for sure.
Good Magazine has some great visuals on resource use, but a cursory search for "water" on their site didn't turn up the goodies I was looking for.
The next time you're on the throne, contemplating that one, ask yourself whether you might be able to divert water flow from your gutters/downspouts to a rain barrel. This is particularly useful if you live in an urban or suburban environment where there is flooding risk - it's a two-fer!
Remember, small changes are important; do not feel unempowered. Individual choices do not compare to industrial use cases, but have other broad impacts; if you think about these issues in your daily life, you will begin to change the behavior of others. In turn, the butterfly effect will manifest, resulting in more and bigger changes for others -- in fact, it already has.