When people steal your layout and claim they didn't know you used/made it.

What grinds my gears is when people do some really stupid stuff.

Something that REALLY grinds my gears is how much HATE generation 5 of Pokemon is getting. Just... I thought it was (mostly) creative...

Something that grinds my gears is when people online use all caps 
and something in real life when people are retarded in public like if I go to the movies someone always has to shout out or say ohh he or she is gonna do this-.-

What grinds my gears, oh let me count the ways:
People that act like complete a-holes, trying to be funny, and act like they're cool when actually everyone hates them.
People that have a "God complex", or think that they're the most important person and everyone should agree with them, for that matter.
When people are sitting practically right next to each other, and they shout their conversation for the entire room to hear.
People who think that their opinions and whatever they say is automatically right, and can't accept anything different.
People that blast their music(any kind) for the entire room, and sometimes outside the room, to hear.
Those people that are... well, "slow", let's say. The ones that need things explained to them a few times, but don't have any sort of disorder or problem, they just don't listen or they zone out or whatever.
People that spit in public, whether it's a wad of gum or just saliva, it's just disgusting.
Stepping in a wad of gum and not noticing until you've already gotten home, and then it gets in your carpet.
People who fart in public, or make sounds like it, trying to be funny.
People that are violent if you don't agree with them or do what they want.
People saying "That's ignorant", or "You're ignorant", and things like that, when it makes no sense to say that the person or thing has a lack of knowledge(the definition of ignorance).

This list is getting a little long, so I'll cut it off here.

When someone bashes my personality with something that isn't true and is assumed.
When I'm stuck behind someone who walks really slow. (I'm a brisk walker, but I live with it)
If someone forces me for an unnecessary favor when I'm doing something very important.
People who deny reality.
People who think against something without knowing the facts.
People who assume things without knowing both sides of a story.
Anyone who shuns true creativity.
People who are physically violent in a casual setting.
Racists and Stereotypes
People who forward crap to me.
A DJ who plays pop music.
People who destroy good morals.
Anti Bieber chants (I don't like him, but chants a immature)
Immature people (see above)
The concept of awkwardness.
The World (Psychologically speaking)

There's a long list...

Hmm, I'm not sure the grind my gears thing is about things that tick you off, more about pet peeves.

So for me,

1. People who talk extremely loudly over their cell phone non stop in public.
2. People who stop together in a shopping isle making passing by really hard because they REALLY want to chat with each other.
3. When fast food restaurants forget to actually give me something I ordered or mess up my order.
4. Whenever ignorant people start spouting nonsense about things they don't get in the first place.
5. People who swarm a You tube channel constantly hating on it content and any new content it creates because they were sent by another more popular channel that made fun of someone else and their content. (I'm looking at you Retsupurae, sometimes the channels you point your finger of execution to aren't bad, they're just not "normal" enough for you.)

Just a few things is all.

I'd say Americans who think they are better to black people and immigrants like me. 
  That and MegaRevolution....

What grinds my gears is when people make promises with no intention to keep them.