The sound of a dart hitting the dart board making funny noises as the opponent is shooting the 9 ball and misses.
7-8 years ago, this actually happened. I was new to pool and had no ettiquitte what-so-ever. One of the local guys lost a bunch of money to my ex playing cards. My ex felt bad and decided he was going to give the guy a chance to make his money back by playing me on the bar table plus give me seasoning at the same time.
The guy was the brother of the owner of the bar we were playing at that particular night. He was a much better player than me, but we played $10 a game even on the bar table. In no time at all I ended up getting up on the guy 8 games. After that we doubled up and I got up on him 8 games again. 3 hours later the guy is aggrivated and we ended up doubling up again for $40 a game. I'm almost up 10 ahead and my ex decides that this is hilarious and feels even more sorry for the guy and says lets just play the last game for everything (which is insane but he didn't want the guy to go bust, just get even).
Stupid me gets bored easily (the entire night I was throwning darts at the dart bored and it didn't make a sound) and while the guy was shooting the 9 ball just as he was about to pull the last stroke, I pick up the dart and throw it to the dart board and the dart board makes a long funny noise

that sharks the guy and he misses the 9 leaving it hanging in the pocket.
At the time I didn't realize or pay any attention to know that was a bad thing to do. I was oblivious and in my own world and didn't think much about ettiquite, sharking or anything of that matter.
Now, whenever I hear the same sound of that dart hitting the dart board, I have to laugh. But now-a-days I do make the effort to be a little more weary of my surrroundings when people are gambling or what not.