What are yours? I have several, although some are making me money:

1. Guys who hang on to high cards too long and are determined to go down with the ship no matter what. Today, a guy raises it preflop to $1, and I call with pocket 7s. The flop comes 345 rainbow. He bets less than pot-sized, I am suspicious and double it. He goes all in for about $9 extra. I am deeply suspicious and call, thinking hey, I have an overpair, a gutshot straight draw, and two outs to the trips. Plus I'm curious, and this feels like a raw bluff. (The "curious" feeling is supposed to be how to lose money in poker, but...) Turn is a blank, river is my third 7, and I win. The hand he mucked (I looked it up thanks to Party's little in-game hand history) was AKo. Going all in with six outs and only two cards to come? Foolish. I don't mind taking his money but you have to wonder how often guys like this bet you off of the winning hand.

2. Habitual check-raisers. They will check-raise anything. The flop could come complete garbage, they'll check-raise you with top pair or even just overcards. Because my natural tendency is to stab at unraised pots, this is one that bugs the hell out of me. If I ID a guy as one of these types of players, I'll stop betting into pots without at least top pair when they're still in the hand.

3. Chronic limpers. People who won't pre-flop raise but will call any raise up to 6X BB with basically any hand. They're eliminating the purpose of the raise. Yesterday I found myself at a pot-limit table with like four of these players - it was really weird. After a while I stopped pre-flop raising and started limping every playable hand, and then just betting when I hit a monster. (At a no-limit table I might have gone the other direction and started really cranking up the pre-flop raises.)

And here's one that used to annoy me until I realized how profitable it was: guys who minimum bet over and over, no matter what they hold. One of these players was minimum betting at me today with a full house. I kept calling with a weak two pair and he made like $1.50 on the hand. That was silly. What I see a lot of is guys with top pair or better betting like that, and guys like me keep calling (because the pot odds are ridiculously good) and hitting weird straights and backdoor flushes. Now I seek out these players. The more of them at a table, the better. They can usually be bet out of most any pot because they don't like big action, and they won't bet you out even when their hand is way better than yours on the flop.