First punch knockdown:

come out of your corner walk towardsyour opponent while holding on the haymaker then when close enough swing the thumb stick back round if you connect your opponent should go down.
Sent in by: danny_blackwood

Burger King Achievement- 100 points Win The Burger King Invitational Fight.

Dodge Achievement - 100 points Win The Dodge Sponsored Fight.

EA SPORTS Achievement - 150 points Win A EA SPORTS Sponsored Fight.
ESPN Friday Night Fight Achievement - 150 points Win Any ESPN Friday Night Fight Event.
ESPN PPV Achievement - 150 points Win Any ESPN Pay Per View Fight Event.
ESPN Wednesday Night Fight Achievement - 150 points Win Any ESPN Wednesday Night Fight Event.
Everlast Achievement - 100 points Win The Everlast Sponsored Fight

Under Armour Achievement - 100 points Win The Under Armour Sponsored Fight.

All venues - Enter "NEWVIEW" as a first name in Create Champ mode to unlock all venues.

Bonus venues - Win a match at one of the corresponding venues in Career mode to unlock it:

Madison Square Garden
The Staples Center - Box as Ko Rey Mo - Defeat Ko Rey Mo in the light heavy division in Career mode to unlock him.

Burger King trainer - Win the Burger King event in Career mode. Then at the trainer selection screen, press Down until the Burger King appears as a choice. He gives you Heart when you fight.

Boxing styles - Win matches in ESPN Classic Fights mode or Career mode to unlock various new styles, at random:

Hard Straights

Hook Master
Judge Jab
Lethal Uppercuts
Philly Shell
Sinister Cross
Slickster
Smooth
Textbook
Uptight

Easy wins in Career mode - Go to the options menu and set "Illegal Blows" to "Off". Then, go to the fight store and buy the illegal head punch called "Elbow Shot". During a fight, use the Elbow Shot to counter attack each time your opponent throws a punch. Note: Make sure you use the Elbow Shot as a counter attack so that you can connect cleanly and powerfully on you opponent's head. You will see that the Elbow Shot inflicts a lot of damage to your opponent, and will KO him in a short period of time, or TKO because you inflicted so much damage to his eyes.

Quick knock out - Swell one of their eyes, then get adrenaline rush and throw hooks. It helps if you are a hook master.

Remain undefeated - During any fight in Career mode, if you get knocked down and you think you are not going to make it, turn your PlayStation 2 off before the bell rings. When the game is resumed, you can start the match again without a loss.