All wrestlers - Press Up(2), Down(2), Left, Right, Left, Right, Triangle(2), Square at the main menu. After enabling the code, go to the options screen and save your options. This will keep all wrestlers unlocked if you start your game over.

Captain Lou Albano - Successfully complete career mode with a wrestler in the "Hated" category. 

David and Michael Von Erich - Successfully complete career mode as Kevin Von Erich. 

Dory Funk - Successfully complete career mode as Terry Funk. 

Fritz Von Erich - Successfully complete career mode as Kerry Von Erich. 

Ivan Koloff - Win the versus tournament. 

Jimmy Hart - Successfully complete career mode with a wrestler in the "Loved" category. 

King Kong Bundy - Win the Southeast Territory in career mode. 

Mr. Fuji - Win the Tag Belts in tournament mode. 

Robert Gibson and Ricky Morton - Win the tag tournament. 

Sabu - Successfully complete career mode as The Sheik. 

Bonus arenas - Successfully complete the game in career mode to unlock the Back Lot, Gym, Beach Resort, and Casino arenas in exhibition mode. 

Real names - When creating a wrestler, you can make people such as Ric Flair, Hall, Nash and others and the announcer will actually say their names. 

Hint:

Increase SmackDown meter - During a match, you can quickly increase your Smackdown Meter until it is full, by pressing Taunt. If your SmackDown meter is almost empty, you will have to repeat this a few times. After every taunt, you will see your meter grow a percentage until it is full. Note: When performing a taunt, it leaves you open for your opponent to attack. This is best performed while they are either groggy or on the opposite side of the arena.

Gameshark Codes

(M) Must Be On 0E3C7DF21645EBB3   0C285977F8A2FC3F 
Enable All Wrestlers 3C6B2603F8FDFFFF 
Max Attribute Points 2C8E6D2DF8FCFE1C 
Max Ability Points 2C8E6D2FF8FCFE1C