#1 The people who don't return a greeting
Let's face it, everyone has problems, if a person cares enough that he keeps his problems aside and wishes somebody luck, night, or morning... that man is giving a positive part as a blessing to you, and not returning a greeting is the worst kind of ignorance and disrespect to the greeter's soul.
#2 People without passion
People without ambition or not even bothering to find their ambition irritate me, and here I am talking about the youth. so no excuses.
#3 People who insult classic movies
I literally worship classic movies, any person who think it's a waste of time to discuss about them hasn't lived his life yet ;)
#4 The negative class :Whiners Snobs Backstabbers and liars
Nearly everyone hates them, whiners don't only suck out your energy, they make you a whiner too... be careful with these people, because complaining has it's limit.
Snobs: No explanation necessary. Humbleness is the best virtue -_-
Backstabbers: The worst kind of the class, even the name sends shivers up my spine, they snuck up until they're close and 'slash' but nothing to worry about, they're usually very weak and stick to backstabbing.
Disclaimer: The following details is just a generalization of some observations in my life, it makes me feel good to swear at them if you are offended in any way, swear it out and pass me the link ;)