Things I've learned from video games:
--Most projectile weapons never run out of ammunition. (Contra, etc.)
--Red overalls are very stylish; even royalty will go for somebody wearing them. (Mario Bros.)
--Teleporters are inherently evil, leading either to hostile alien worlds, or possibly even hell itself. (Doom, Half-life)
--That fat, stupid kid who lives next door? Yeah, he's plotting to enslave humanity. (Earthbound)
--Farming is a fun, easy, and very lucrative endeavor, and gives you access to all the most eligible bachelorettes in town. (Harvest Moon)
--If you yourself get carjacked and go after the guy who ripped it off, the cops are going to try to kill you. Likewise if you beat up someone who just mugged you in front of the police. (GTA2)
--The Nazis invented all sorts of futuristic weaponry and even managed to both reanimate the dead and enlist the aid of the undead in their effort to take over the world. (Wolfenstein)
--If you're in really good health and swing a sword around, you can actually shoot energy from its tip. (Zelda)
--Swordsmen do well in battle against axemen, axemen do well against spearmen, and spearmen do well against swordsmen. (Fire Emblem)
--A very powerful blow with a weapon is actually a matter of luck, rather than any indication of one's skill with a given weapon. (Pretty much any RPG ever).
--Hedgehogs are blue, and only have spikes on their head. (Sonic)
--Most soldiers can only see objects about 10 meters ahead of them. And their weapons are not up for grabs, either. (Metal Gear)
--Capsules full of liquid nitroglycerin are a perfectly acceptable means of powering elevators. (Resident Evil)
--If you regularly use elevators to get around your place of employment, be careful! You may get inexplicably stuck in the floor. (Half-Life)
--One man will often fare better against impossible odds than large armies (many games)
--Roman citizens are a bunch of blithering idiots who never walk where you want them to, goddamn it. (Caesar 3)
--All power plants last for exactly 50 years, and then spontaneously combust. (SimCity 2000)