Basically What Makes You Mad.
What grinds your gears?
When I got the munchies, but have no munchies.
When people lie to my face :mad:
When people think they can just grab my stuff from right in front of me and look at it/use it without asking me first.
What grinds my gears? Poor alignment, excessive torque, or lack of lubrication, mainly.
Sorry, had to 
When people say bad stuff about my best friend right in front of me