The biggest tool in harness racing? That's an easy one, the bettor! I realize this answer is not in the spirit of how this question was asked but... With the drugging of horses, the stiffing of horses, the fixed races, the small pools, the high takeouts and low payouts, it is the bettor who is the real tool. Unless you have real inside information or you're allowed to bet after the race goes off, you are the mark at the poker table. Within that same theme, there's an old quote that goes something like "if you don't know who the sucker is, it's you!".