How to handle rude and distracting fellow graduate student who sits in the same office? In a nutshell, I hate one of my fellow PhD students. I am sitting in the office with that fellow graduate student who frequently interrupts me when I want to focus on my work. He also often is very insulting to me in front of other fellow graduate students.

I general, I try to be nice and respectful to my fellow students, but I suspect this makes me a perfect target to him. Also he seems very nice to other people, just not to me. I wish I could change the department because its actually a major drawback and affects my whole PhD life, since I currently meet him every day all the time. I frequently miss lunch or some activities of my lab, since I know I couldn't handle his presence. But I don't want that my social life suffers because of him. Do you have any tips on how to overcome this situation successfully?
A friend once told me that people take from you exactly what you choose to give them. In other words, this person manages to distract you because you let them. Similarly they manage to annoy you with their rude behaviour because you let their insults get to you. Therefore, I am going to suggest you a nice change of approach, rather than a change of office. 

IMHO the best way to tackle distractions is to ignore them. My experience shows that a large pair of noise-cancelling headphones coupled with a focused look that never leaves whatever it is you are doing, work miracles in this case. 

Whenever I need to focus and lock myself in the zone, I gear up and ignore everything that happens around me. If people ask me questions, and I actually manage to hear/see them, I tell them, swiftly and politely, that I'll be with them once I finish whatever it is I am doing. Your body language is extremely important while doing so. You want to make sure that you show that you won't be leaving what you are doing to deal with them, because you deem that what you are doing is more important. For example, I don't remove my headphones to answer, and go back to my task straight away. In addition, once you adopt this technique, be democratic and use it with anyone and not just this particular person who distracts you.

Make sure that you show that you are actually focusing on work rather than on leisure. Human psychology 101 suggests that if someone sees that you appear super-concentrated whilst in reality you are browsing social media they will feel allowed to disturb since they will think that you're not actually working. You have the right to not be disturbed whilst you are on a break, however the fact that you are taking a break implicitly says that you are free and can be disturbed.

Interestingly enough, the ignoring technique also works for rude behaviour and insults. Nothing clips one's wings more than instantly getting the feeling that one's behaviour has little or no effect. For your own sake, I'd suggest you begin by ignoring the rude comments that hurt you. This will not be easy at first, but you'll feel the benefits as you get better at it.

Now, nobody should be forced to feel like you do. What you describe is prototypical bullying. Bullying should have no place in life, let alone academia. The steps I would follow would be to begin by talking to this person telling them you would like them to stop with their rude behaviour. Although they might be joking you can't seem to tell whether that is the case, and think that the problem will be solved if they stop whatever it is they are doing. 

After talking to them, wait some time. If the behaviour persists then escalate the complaint to your supervisor, the team/department head, or whomever you think has the authority to deal with this. The important thing is that you remain calm and polite during your interactions with your colleagues. Last thing you want is for others to accuse you of being rude.