To get goku to do a spirit bomb: Press right, left, down, up.
(this only works with normal goku, not super saijan)
Send in by Domizcool

To get gotenks: - Beat the game on hard 9 times and when you do go to the character selection screen and press select 9 times on miria trunks non super sayin
Sent in by Nofloors4me@cs.com

Extra characters:-  Press Right, Left, Down, Up, Right, Left, Down, Up at the "Press Start" screen to unlock extra characters. Then, press Triangle(5), X(9).

Random tournament participants:-  Select tournament mode, then press Start at the character selection screen. 

Super attack:-  Press the D-pad a quarter-circle backward and forward, then press Triangle.

Meteor:-  Hold Forward and press R2. Your character should perform a kick. When you kick your opponent, press Triangle + Square, Triangle + X, or Triangle + Circle repeatedly.

Unblockable attack:-  Press R2 + Triangle + X while in front of your opponent. You may also do a super hit by pressing X near the opponent. 

Counter Kai attacks:-  There are four ways of countering Kai attacks. When a Kai attack is fired, you will see a small box in the left corner that reads "Counter". You must press the correct buttons continually before it appears.

Press Square + Circle to hit the Kai blast away from you. Note: You will lose a little life. 
Press Triangle + X to make a small bubble go around you and block it. Note: You will lose a little life. 
Press X continually and you will only get half the damage. 
Fire a Kai Blast back by pressing Triangle + Circle + Square. The Kais will hit together. Keep pressing Triangle as fast as possible and it will hit your opponent. If not, you will receive regular damage. 

Counter demo attack:-  As soon as your opponent starts a demo, repeatedly press Square + Triangle + Circle. If done correctly (not too fast or slow), you should counter.