In my opinion, two of the worst characteristics one can have are arrogance and stupidity...arrogance because one always thinks he knows what's best and stupidity because he rarely does. What two characteristics,existing in one person, drive you bonkers?

Talent and narcissism. You see this a lot in the world of professional athletics, where supremely gifted individuals ruin their careers by engaging in drugs, violence, promiscuity, etc.

i think you said it all but i can add know it alls and nonlisteners.

I can live with arrogance, but I absolutely cannot tolerate stupidity, and especially willful stupidity.

Selfishness, and the use of an ability to Manipulate. NOT A GOOD COMBINATION.

sectarianism, and vanity

Holier-than-thou, and judgmental. http://www.urbandictionary.com/define.php?term=holier-than-thou

Um , mine would have to be people who think they can school you on everything- even if they know it's not true! another would have to be cruelty, I try to love, it just gets hard.

Arrogance is like my #1 all time thing that annoyes the piss out of me! So, Arrogance and... Well, like you said- stupidity.

Arrogance and stupidity are the same thing. One cannot exsist without the other. This person thinks he knows everything, but is to stupid to realize no one does.