Actually, the reasons for to anger a loved one guy, may be many. Ещt more reason appears, if the guy is not a favorite, as well. You can piss off a person with the aim to help him, just to show him who's boss, as a joke. But if you took this case, consider the temperament of your friend. If you don't know him well, better not Wake this beast. Someone quickly "boil" and just as quickly cools down, and someone might have in anger to hurt. So in any case do not forget about safety precautions.
Suppose you decided. One of the surest ways for someone to piss off is repetition (just like ass fool) everything that someone says. You probably have a chance to try it for yourself. This will not get and do not go away: often to get people to stop repeating, you have to get angry and yell, and you just do something and achieve.
Also very angered constant jokes. Some people may be tolerant of one or two jokes, but if they are repeated from day to day (and choose not some harmless jokes, but the real evil stuff), and if the object of ridicule it will be clear that this is the work of your hands, it's unlikely that your friend will stand with a calm heart. If you can do it, then he's either a Saint (then drop all attempts - all the same will achieve nothing), or... Well, you can continue to offer themselves.
Play on the interests your guy. The most explosive topics would be politics, military history, religion - it all depends on the guy. If you decide to piss him off, just join him in debate on one of the dangerous themes and bend the line to the red mark, after which begins the worst. The main thing for you in this situation is to remain calm, you want to make him angry, not to angry myself.
Whatever goals you may pursue, remember that there is a limit. Emotions are a dangerous thing, you never know where it might lead. People may not understand your hint, get angry and walk away, deciding not to waste time on such boring. Of course, it may be, and Vice versa: sometimes shaking up the right people, especially those that can accumulate the emotions in themselves, not knowing that this negativity is poisoning them. But still be skilled psychologists start from the position of use. Of course, if you don't want to simply get rid of the man.