BALLS!

    Source: http://www.oddballs.co.uk/juggling-balls-stage-balls-c-1190_2170.html

 Ok, there. I said it. And what a fun word it is!
Balls is SO great because of its versatility.

Obviously, it can be used as a noun (with several connotations, no less): "Where'd the ball go?" OR "Is that the guy with the old balls?!"
It can be used in an exclamatory way: "Balls!"
It can be used as an adjective: "This party is balls."
It can be used as a colorful noun in a simile: "It is hot as balls out there!"

Balls can be used as a weapon: "He was a terrible pitcher! He hit me twice with his balls (TWSS)!"
Balls can be foul (in more ways than one): "Foul ball!"
Balls can be fun...when you get to dress up in your finery and partake in a dance or two (get your mind out of the gutter).

I'd go on, but I don't want to bore you with my balls rantings.

In short, balls are fun to talk about, but that's pretty much the extent of their appeal. Unless you are a 3-5 year old or a man over the age of 13...in which case, you probably really enjoy playing with balls.