What do you do if your best friend is annoying and irritating now?

Well, first of all, you might want to talk to him or her about it. Tell him or her that you find them annoying, and tell them what it is that annoys you. Also, try putting yourself in your friend's shoes. Try to see if you are actually doing it deliberately or maybe if he or she might have issues. If he or she is only annoying for a silly reason, such as an annoying laugh, it isn't them who is being annoying, it is YOU for being so shallow and cliquish.