What are some unwritten rules in baseball that most every player follows? Mine is not swinging on a 3-0 count...

No stealing a base or taking an extra base if the play will be close when the score is a blowout (this, of course, is subjective and depends on the ballpark).

If in Wrigley Field, throw home run balls back if they are from the other team

I would have to say that one is, If the other teams pitcher hits one of your guys, then your pitcher should hit one of their guys. That should be it after no more bleeding fights I get tired of them sometimes.

not slapping the ball out of an opposing player's mitt (cough cough a-rod cough cough)

Thats not a cough, more like an asthma attack

lol

we need to get that checked