Water Tower Down

A common method used in order to Kill It With Water. See that water tower on top of the building? Well, it turns out these are - ahahaha - filled with water. Knock down the water tower, and a huge torrent of the stuff will come crashing down below. It will displace and pummel any living thing beneath it, and extinguish fire extremely quickly. In a fantastic setting, water-weak creatures will often be wiped out by it. Try not to think too hard about why a water-weak opponent would choose to fight anywhere near a water tower.

Comic Books

 * Nite-Owl and Silk Spectre take advantage of one of these to temporarily subdue a fire in Watchmen. It keeps going, but the water clears enough of a path for them to rescue the apartment tenants.
 * Buffy the Vampire Slayer tie-in comic Viva Las Buffy Buffy is combating vampires on a rooftop. Realizing she's outnumbered, she tosses a conveniently nearby priest into the rooftop water tower and tells him to bless the water. He does so, and Buffy knocks down the tower so the vampires disintegrate from exposure to the now holy water.
 * Occurs in the first issue of Untold Tales of Spider Man, where an inexperienced Spidey fights The Scorcher (an armored arsonist) in a warehouse.

Film - Animated

 * In Looney Tunes Back in Action, Daffy Duck causes DJ to run the Batmobile into the Warner Bros tower and knock it over, flooding a few scenes, ending the chase scene, and getting DJ fired.
 * Used by Rango (accidentally) to take out the hawk. Because it's empty, he drops the tower itself on his enemy.
 * Happens to Ludmilla at the end of Bartok the Magnificent.

Film - Live-Action

 * This is how the Sandman is taken out at the end of the third Spider Man movie.
 * At the beginning of the Wild Wild West movie, one of these is knocked out in the middle of an arrest attempt. Things go badly from there.
 * In the original Highlander film: the Kurgan slashes out the supports of a water tower on the top of a building in order to give him extra cover from which to ambush Connor Macleod (they are fighting on the roof at the time).
 * The ending of The Towering Inferno has the heroes blowing up a set of huge water tanks at the top of the building in an attempt to extinguish the fire.
 * Mr  is thrown through a water tower in Dark City.

Literature
"''"In the event of your not doing so, the Lord High Provost of Notting Hill desires to announce that he has just captured the Waterworks Tower, just above you, on Campden Hill, and that within ten minutes from now, that is, on the reception through me of your refusal, he will open the great reservoir and flood the whole valley where you stand in thirty feet of water. God save King Auberon!"
 * One of these is destroyed in an assault on a Japanese-held Australian town, killing a spotter team on it, in Alternate History novel Designated Targets.
 * In GK Chesterton's The Napoleon of Notting Hill, threatening this is how Wayne finally gets his enemies to surrender. Indeed, Chesterton described the use of the Waterworks as a weapon as part of the original inspiration.

Buck had dropped his glass and sent a great splash of wine over the road.

"But--but--" he said; and then by a last and splendid effort of his great sanity, looked the facts in the face.

"We must surrender," he said. "You could do nothing against fifty thousand tons of water coming down a steep hill, ten minutes hence. We must surrender. Our four thousand men might as well be four. Vicisti Galilaee! Perkins, you may as well get me another glass of wine."''"

Video Games

 * Suikoden V has Lucretia flooding an entire castle in order to kill the enemy mooks inside.
 * In Baldur's Gate the cloakwood Mine was abandoned when the miners dug into a riverbed. Years later the Iron Throne somehow got the hole sealed and the water pumped out, to resume the mining with illegal slaves. After killing the local leader in charge of the mine, you take his key to the seal and then you can figure out the rest...
 * In the first fight against Doppelganger in Maximum Carnage, it's possible to instantly defeat him by throwing a nearby water tower at him.

Western Animation

 * This is the method by which the Teenage Mutant Ninja Turtles Splinter first defeats the Shredder in the second cartoon; not only does the water throw him from the rooftop, the tower itself then lands on him. Ouch.
 * Variant in the Batman the Animated Series "See No Evil": when Batman is fighting an invisible opponent under a water tower, he throws a Batarang into the tower's underside, causing water to leak onto his foe and make him visible. (The man is still taken out by Batman's martial arts.)