So when I'm not at school, I install 12 volt car accessories (starters, stereos, GPS systems, etc). One of the most common things we have is people coming in with 5-10 year old remotes wondering why they aren't working. My first question to them is usually "When was the last time you changed the battery in your remote?" The most common response is "IT HAS A BATTERY!?" or "It's only X years old, it shouldn't need a new battery!" I then tell them that they should be replaced every year, which we usually tell them when we install.
Another, less common thing that people ask, but far more stupid, is "So does the car use gas when I start it with the starter? You know, cause the key isn't in the ignition" or a variant "What's the gas milage on a starter?"
Fuck, I could go on for hours about the stupid shit people say. People are stupid as shit.