Dragon Ball Z Budokai 2

Beat Supreme Kai with Goku to unlock him.

This isnt really a cheat but this is how you taunt first you have to get into a battle then hold punch, guard, kick and energy together at once then your character will do a taunt but, the cool thing is that it brings your opponent down one ki gauge if successfull.

To train with Elder Kai, beat King Kai's level.

To train with Goku, beat Elder Kai's level.

To train with Kami, complete Korin's level.

To train with King Kai, beat Kamis level.

To train with Korin, complete Master Roshi's level.

Go to Edit skills menu. Then Edit capsules. First, with just about any character, equip"Gero's perpetual energy". Then equip "dende's recovery" and "mixed Blood Power".

Note 1: This isn't much of a cheat but a good strategy.
Note 2: You won't be able to transform!

Wish for the skill from Shenron after finishing DragonWorld.

You automatically unlock Gotenks on Stage 10 when Goten and Trunks fuse.