I am the king of insults.
If you get into an argument with me, I can murder anyone with my repetoire of insults.
Firstly: Your mum! While it may be basic, and everyone knows it, just chuck it in there while having an argument and it's sure to stop them in their tracks.

Secondly: Your face.. on toast!--The correct usage is the same as "your mum" but must be timed properly, only expert insulters know how to use this. You must wait for the initial shock of you shouting "your face!" at them to end, and just as they are about to come up with an (undoubtedly shit rebuttal) you say "on toast!". A little known fact is that this started the Cold War.

Now this is the insult reply for beginners and pros alike: if you get insulted you simply reply "I know you are, you said you are, but what am I? And if you say the same thing back to me, you're a chimpanzee". Everyone can use this to great effect, highly recommended against everyone.

Now here we come to one of the more potent insults: You big fat poo poo head. Yes, that's right, I resorted to the wit of a 4 year old. The dangerous thing about this is that everyone can use it to massive affect, use wisely.

And finally, it comes to the most potent insult of all, now you should never, ever use this insult unless faced with to prospect of actually losing the fight. This insult can literally kill people. Especially with correct useage.
What you must do is say it thusly (in a deadpan manner) "You, sir (even if it's a girl) are a blowjob."

Say it with as little emotion as possible.
You can not come back to it, it is impossible, and you can replace "blowjob" with any manner of sex acts such as "wank", "bukkake" or even "arse felching"

If you have got this far, then congratulations, you will now win any argument you're faced with, or lose all your friends, either way it's win-win!
(River of Squid has a variety of lemons in his pocket, Thu 4 Oct 2007, 14:37, Reply)