Why is there always one no it all jack ass in every university lecture / tutorial?  

Have started a bachelors degree in Defence Studies at Massey.  (Turns out recessions reduce job prospects for unskilled, un-educated people.)  The class is pretty cool, bout 6 Kippenburger officer cadets, few ex military guys and some random arts students.  But there is this one know it all random "look at my massive collection of guns" guys who goes home at night and watches DVD's of tanks.  I just want to hit him right in the jaw.

But its not just now.  In almost every class I have ever had there is always one guy that just has to try and get one up on the lecturer, interrupt classes, argue with classmates in a non-constructive way, make loud stupid jokes that no one gets and are just general weirdoes.

Is this just an arts thing, or are they in all classes?  Anyone else had any esperiences with these kind of people?