An interesting thing I learned about CS is that the guns have a consistent pattern to their bullet spread. When you fire an entire clip with automatic fire, the bullets are not laser accurate of course, some bullets go left, some right, etc. Well, the pattern by which the bullets are off is consistent. The second bullet always goes right, the third always goes left, etc. This means if you practice enough you can learn to move your mouse just right to compensate and land every bullet exactly where you want... at least in theory, but I don't know if anyone is actually that good. I've always thought it was interesting game design that skill could overcome bullet spread though.