Select a pitch, then hold R1 and press X when choosing between a ball or a strike. Note: Doing this repeatedly will result in your pitcher getting ejected from the game.
Cheat mode
Pause game play and press Square(2), Circle(2), L1, R1. A sound will confirm this portion of the code. Then, press L1 + L2 + R1 + R2. The "Ball Cannon" (set pitch physics) and "Game State" (edit game parameters) options will now be unlocked.
Eject other team's best players
Use two controllers and hit the CPU player. Have him charge the mound. When he is ejected, the CPU will not have as many good players.
Fights
Hold Square after your batter is beaned and he will charge the pitcher and start a fight. Your player will be ejected. Alternately, hold R1 + L1 + R2 + L2 after your batter is beaned and he will taunt the pitcher. While continuing to hold those buttons, hold X to will charge the pitcher and start a fight. Your player will be ejected.
Restore pitcher's stamina
When you are at the game menu screen just before starting a new game, return to the main menu. Then, go to the game menu screen again. One of your pitcher's stamina will be restored. Do this repeatedly to replenish your entire pitching staff's stamina.
Bean the batter...