A Prisoner's Dilemma

Do most people here know about this game? (If you do, you can skip the next paragraph.)

Basically, you have two people playing each other, and the objective is to get as many points as possible (but not necessarily more points than the other person, if I understand right). Each person can choose either to cooperate or defect, and they can't see what the other one chose before making their choice. If both cooperate, than they both get 3 points. If they both defect, than they both get 1 point. If one cooperates, and the other defects, than the defector gets 5 points and the cooperator gets none.

Anyway, strategies for this are generally not geared towards beating or penalizing the other person, but towards getting the most points for yourself (that is, to cooperate). My compsci prof built a program which took a number of simple AI personalities and paired them off in a round-robin sort of a deal and had them play a tournament, to see who wound up with the most points. Each personality utilized a different strategy. He started with:

1. Just Mean: Defects every round.
2. Look Back: Responds with the other player's last move.
3. Absentee: Cooperates for the first two rounds, and thereafter defects only if its opponent defects twice in a row.
4. Pavlov: Cooperates the first round, and then cooperates if it and its opponent chose the same option in the previous round, and defects if they chose differently.
5. Gotcha: Does the same thing as Look Back, only defects for no apparent reason in turns 40 and 60.
6. Tester: Defects in the first round, cooperates in the second round, and continues to switch until the other player defects - than it does the same thing as Look Back.
7. Friedman: Cooperates until the other player defects, and then defects every subsequent round.
8. Punisher: Cooperates, until the other player defects. The first time that happens, it defects in the next round only; the second time it defects for the next two rounds, and so on.
9. Forgiver: Begins by cooperating, then keeps track of two totals: a) how many times the other player has defected in response to Forgiver cooperating in the previous round, and b) how many times the other player has cooperated since last defecting in that way. If a is more than one greater than b, Forgiver defects; otherwise, it cooperates.

Anyway, I've got the program on my computer, and I've run it and seen the results of the tournament. I thought it would be fun if I posted it here, and people could try and guess who would win.

I also wrote a few strategies myself, if anyone wants to see those in action - and if someone thinks they have a better strategy, I can code it and run that in the tournament too.

Edit: Forgot Friedman. Whoops.