Students who cheat on exams and don't even try to be discrete about it.

Don't think I didn't see you pass that paper to your friend sitting next to you.

People who ride bikes/scooters on the sidewalks on campus.

Not trying to die by getting run over by you today, thank you very much.

When the person sitting next to you during an exam has a runny nose and sniffles the entire time instead of using a tissue. 

Didn't your mom teach you how to blow your nose when you were four?

People who eat their entire lunch during class every day.

I really love trying to concentrate on financial accounting while you're chomping in my ear.

The person who's hacking up a lung in class and seems incapable of covering their mouth. 

Are you TRYING to start an epidemic?

When groups of people take up the entire sidewalk and walk at a speed that's slower than molasses.

You always seem to encounter these people when you're running late for class.

Professors who factor grammar and spelling on papers into your grade but make typos in the assignment directions.

Practice what you preach.

When you're in the library and the person next to you has the volume on their music turned up so loud that you can clearly hear every word through their headphones. 

The purpose of headphones is so that the people sitting around you DON'T have to listen to your music.

When someone takes your seat in class in week eight.

There aren't technically assigned seats in college, but we all know that once someone claims a seat, you don't take it.

 The slacker in group projects. 

I really love working my butt off so you can get an easy A.

 Professors who refuse to let you out of class early, even when they've finished the lecture material.

"Now let me spend the last 15 minutes of class lecturing about a topic that has nothing to do with class because I have an hour and 20 minutes and intend to use every minute of it."

 People who walk on the left side of the hall/sidewalk/stairs.

Everyone knows you're supposed to keep to the right.

 The know-it-all.

You know the type. They're also the ones who suggest to the professor that the class would benefit from more exams.

 Professors who want assignments single spaced. 

For some reason two pages double spaced seems much more manageable than one page single spaced.

 People who don't hold the door for you.

It's called being polite.

 When professors don't post grades online. 

It's really not that complicated.

 Students who think they own the town because they drive a fancy car.

No, you are not in fact exempt from following the speed limit on campus just because you drive a Porsche.

 When it's week ten and your professor still doesn't know your name in a class of 20.

I'd get it if it was a 200-person lecture, but is it really that hard to learn 20 names?

 People who smack their gum in class.

The sound of your gum is overpowering our professor's voice.

 Group projects when you don't have any friends in the class.

Thank you, Professor, for making me announce to the entire class that I have no friends.