Mr. Aggressive is sitting to your right. He's annoying. All checks to him are bet, regardless of how pathetic the cards look. You know he has nothing and would like to put him in his place. Unfortunately you don't have anything. But enough is enough and you call him to showdown, surely your ace high will win. Alas Mr. Aggressive pairs up to beat with you threes.

The Sheriff

In one of Hellmuth's book he uses the expression "to play the sheriff." It refers to home games where one person feels compelled to call a bluff for no reason other than to expose the bluffer. While perhaps more likely in friendly games it certainly exists elsewhere, such as low limit tables frequented by play anything maniacs. Seeing this nut win hand after hand with bluffs angers other players. They want to stop him.

Straight away comes the first problem. Poker is a game that needs to be played cold and emotionless. Anger, as well as joy, will do nothing but cloud judgement and lead a player to making the wrong decisions. Targeting a player should be done for no other reason than to exploit their weaknesses.

Annoying, sheriff-needing players tend to have several exploitable weaknesses. These are players which play too many hands. These are players that always raise on the button. These are players that raise a bet for solely to test one's sincerity. These are weaknesses.

The Gun

An opportunity to act comes any time a bluff has been clearly identified. This observation alone is not enough to decide how, or even if, one should act. There are several other factors which need to be considered. To reiterate the above, the desire to punish is not a legitimate decision criteria.

Position is, as per usual, a strong deciding factor. Without a strong hand a player in mid position should probably not call the bluff. If there are still several players in the late position who aren't maniacs it'd be good to know first their intentions. Late position, and especially last position, is the right time to act on a bluff.

It comes down to the cards now. Though the bluffer is likely to have a weak hand the sheer randomness of the shuffle will cause a frequent hit on one pair and occasionally two. Playing ace high against them is not a wise idea. A terrible hand remains terrible even up against a loose player. Here is the key point to be made: never call a bluff with garbage!