Android 16:
You can find Android 16 at Plain among the south island. Bring him to Bulma in West City (Krillin's Dragon Universe mode the second time).
Information in this section was contributed by chris warrilow.

Android 17:
Defeat Android 17 as Piccolo in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Android 18:
Successfully complete Dragon Universe mode as Krillin.
Information in this section was contributed by chris warrilow.

Bardock:
At the start of Dragon Universe mode, fly over to Raditz's spaceship. You should see a "???". Enter it, and you should get him.
Information in this section was contributed by chris warrilow.

Alternately, keep checking the Sayian Space Pod, and at one point you will be able to go to it and find Bardock. This was found near the end of story mode when playing the first time.
Information in this section was contributed by Mark Rivenburgh.

Brolly:
As Goku, complete Dragon Universe mode at least three times. On the third time, you will fight Brolly. Defeat him to unlock him.
Information in this section was contributed by renick9247.

Go to the Desert/Mountains and speak to Kibito southwest of the next marker. After you fight Buu inside himself, Goku and Vegeta will sense a different energy. Then, go to the next marker to face Broly. Defeat him to unlock him.
Information in this section was contributed by chris warrilow.

Captain Ginyu:
Defeat Captain Ginyu as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Cell:
Defeat Cell as Teen Gohan in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Cell Jr.:
Defeat Piccolo in Dragon Arena when he broken in. Note: You must be at level 20 to 40.
Information in this section was contributed by chris warrilow.

Cooler:
Defeat Frieza. SS Vegeta will appear under the location where he was defeated. After defeating SS Vegeta, go to Cooler's red dot. Defeat Cooler to unlock him.
Information in this section was contributed by chris warrilow.

Dabura:
Defeat Dabura as Gohan in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Dr. Gero:
Defeat Dr. Gero as Yamcha in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Frieza:
Defeat Frieza as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Gogeta (Vegeta):
Bought from Skill Shops (random) when you have the Black Membership Card.
Information in this section was contributed by chris warrilow.

Alternately, play as Vegeta in the second Dragon Universe. In the Buu Saga, you should find Bulma in a plain somewhere. Talk to her, and she will tell you to visit her later. Then, fly to West City. Pick up the present she has for you (Super Sayain 4). Next, fly to the red dot to the south. Once there you will meet Super Sayain 4 Goku. Defeat him and you will get the capsule for Gogeta.
Information in this section was contributed by Damon Cooper.

Gohan:
Successfully complete Dragon Universe mode as Teen Gohan.
Information in this section was contributed by chris warrilow.

Goten:
Defeat Goten as Gohan in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Gotenks:
Bought in the Capsule Shop.
Information in this section was contributed by chris warrilow.

Great Saiyaman:
Successfully complete Dragon Universe mode as Gohan.
Information in this section was contributed by chris warrilow.

Hercule/Mr. Satan:
Help him out in Piccolo's Dragon Universe mode (Majin Saga) at the desert, and talk to Videl at Central City.
Information in this section was contributed by chris warrilow.

Kid Buu:
Defeat Kid Buu as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Kid Goku:
As Goku in Dragon Universe mode, at the beginning look for someplace that reads "Grandpa Gohan's house". After you go to it and Goku talks to his grandpa, you will unlock Kid Goku.
Information in this section was contributed by Mark Rivenburgh and steve renick.

Alternately, successfully complete Dragon Universe mode as Brolly.
Information in this section was contributed by chris warrilow and jaspal singh.

Kid Trunks:
Defeat Majin Buu as Vegeta in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Majin Buu:
Defeat Majin Buu as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Omega Shenron:
Once invited to fight against Gotenks at the tournament in Dragon Universe mode, visit Bulma in West City. Defeat Gotenks to unlock Omega Shenron.
Information in this section was contributed by chris warrilow.

Recoome:
Defeat Recoome as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Saibaman:
Defeat Nappa in Dragon Arena when he broken is in. Note: Your level must be between 10 to 20.
Information in this section was contributed by chris warrilow.

SSJ2 Gogeta:
After defeating Broly in Dragon Universe mode, defeat Gotenks at the World Tournament Arena.
Information in this section was contributed by chris warrilow.

Super Buu:
Defeat Super Buu as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Supreme Kai/Kaioshin:
You can find him at the plain before you go to the last battle in Gohan's Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Teen Gohan:
Successfully complete Dragon Universe mode as Kid Gohan.
Information in this section was contributed by chris warrilow.

Trunks:
Successfully complete Dragon Universe as Vegeta.
Information in this section was contributed by chris warrilow.

Trunks (young):
Defeat Majin Buu in Dragon Universe mode as Vegeta.
Information in this section was contributed by chris warrilow.

Uub:
When fighting Kid Buu, use the Spirit Ball technique and win.

Vegeta:
Defeat Vegeta as Goku in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Vegito (Goku):
Defeat Super Buu as Goku in Buu's Body in Dragon Universe mode.

Vegito (Vegeta):
Defeat Super Buu as Vegeta in Buu's Body in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Videl:
Go to the Plains as Gohan in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Dragon Radar:
Keep looking all around the map as soon as you start. Pick a point and go in a small angle so that you move out just a little bit at a time. You will see a marker appear with "?????". This may take some time, and you may find some money or capsules, but you will find the Dragon Radar along with two Dragon Balls in the first area. Do the same type of search pattern on each area to find everything; even places to fight and level up, along with friends who will give you skills and even a level up or two.
Information in this section was contributed by Mark Rivenburgh.

Gogeta capsule:
Play Dragon Universe mode as Goku or Vegeta. Continue until you will get an invitation from Goten and Trunks to fight in a fusion battle instead instead of fighting Buu or Brolly. Win the fusion battle to get the Gogeta capsule.
Information in this section was contributed by jaspal singh.

SSJ4 Gogeta Fusion:
On the Majin Buu map, defeat Omega Shenron as Goku.

SSJ4 Gogeta Fusion:
On the Majin Buu map as Vegeta, enter all the red dots and other areas beside the red dots after every red dot event.

SS4 Goku:
Have 30,000 Zeni and go to the Skill Shop It will rarely appear. If you win the Adept or Advanced Tournament first, it may appear sooner.
Information in this section was contributed by Frankie.

After defeating Kid Buu with the Super Spirit Bomb, and before you go to fight in the World Tournament, go to one of the islands just north of where the compass is on the map. You will see a "???". Land there and you will get SSJ4 for Goku. Note: You may have to complete Dragon Universe mode a few times before you do this.
Information in this section was contributed by Coldmoon001.

SS4 Vegeta:
Buy it at the Skill Shop for 30,000 Zeni (randomly), after you get the Black Membership Card.
Information in this section was contributed by Frankie.

Super Sayain 4 Goku skill:
Note: You may need to complete Dragon Universe mode first. After your first fight with Buu to your last fight with Kid Buu, search the entire map after each fight. At some point you will find Goku's Super Sayian 4 skill. This has happened just before fusing with Vegeta to fight Super Buu, and it appeared as a "?????" at the bottom right area. However, this may vary from game to game.
Information in this section was contributed by Mark Rivenburgh.

SSJ4 Vegeta Transformation capsule:
On the Majin Buu map, go to West City as Vegeta to see Bulma.

Bonus items:
Have a saved game from Dragon Ball Z Budokai 2 on your memory card to get a Silver Membership Card, Babidi's Pot, and Bardock.

Membership cards:
These are located in Goku's Dragon Universe. All three membership cards can be found on an island just north of the "Golden-Gate" looking bridge. After going through Goku's Dragon Universe a few times, all three will be there to be collected.
Information in this section was contributed by chris warrilow.

To get all membership cards, look all over the map and get all the "???" items. At some point you will find a Black Membership Card. Go in there again and you will get all the membership cards.
Information in this section was contributed by Tuan Nguyen.

Dragon Balls:
Find the Dragon Balls in Dragon Universe mode as follows, and you can wish for a Breakthrough Capsule, Memories, or some rare Green Capsules.
Information in this section was contributed by chris warrilow and renick9247.

Two Dragon Balls are in Saiyan Saga (Earth)
The first ball is by the white plains; around Red Ribbon Army Base.
The second ball is between the upper two main islands.

Two Dragon Balls are in Frieza Saga (Namek)
The third ball is at the upper right island.
The fourth ball is on the left island near map border, southwest of the upper left island.

One Dragon Ball is in Cell Games (Earth)
The fifth ball is found where the compass is on the map in the water.

One Dragon Ball are in Buu Saga (Earth)
The sixth ball is by the main island towards the middle by North City.
The seventh ball is at a little sandbar island (resembles a beach) near the martial arts tournament.

Baba Crystal Balls Movie 00:
Unlock all Ultimate Move skills and the Baba Crystal Balls Movie 00 will now be available for purchase at the Skill Shop.
Information in this section was contributed by chris warrilow.

Baba Crystal Balls Movie 01:
Buy the Baba Crystal Balls Movie 00 and the Baba Crystal Balls Movie 01 will now be available for purchase at the Skill Shop.
Information in this section was contributed by chris warrilow.

Breakthrough (All Character):
Can be bought for 75,000 for each character at the Skill Shop after you have Baba Crystal Balls Movie 01 and get all Breakthroughs for each playable character in Dragon Universe mode.
Information in this section was contributed by chris warrilow.

Ultimate Skill Moves (All Character):
Can be bought for 50,000 for each character at the Skill Ship after you have unlocked all characters.
Information in this section was contributed by chris warrilow.

Dragon Arena:
Successfully complete Dragon Universe mode with all unlockable characters in that mode, including Broly, teen Gohan, and high school Gohan.
Information in this section was contributed by Top Two Percent and chris warrilow.

Grandpa Gohan's House:
Play as Kid Gohan in Dragon Universe mode, the second time through. Instead of fighting Piccolo in the Mountains, go to Grandpa Gohan's House and defeat Goku.
Information in this section was contributed by chris warrilow.

Cell Games Tournament:
Defeat Cell when he appears in the Dragon Arena matches.

Hint: Dragon Rush:
Use the following trick to win in Dragon Rush about 80% of the time in every match. If you start Dragon Rush, first: X; second: Triangle; third: Square. If your opponent starts Dragon Rush, use Square, Circle, or X.
Information in this section was contributed by Gogetenks.

Hint: Special versus matches:
Before every match (except Dragon Universe and Arena). almost every character has a special scene. The list is as follows:
Information in this section was contributed by Gogetenks.

Goku vs. Vegeta
Goku vs. Frieza
Goku vs. Bardock
Goku vs. Brolly
Kid Goku vs. Tien
Trunks (Adult) vs. Vegeta
Kid Goku vs. Piccolo
Kid Gohan vs. Piccolo
Teen Gohan vs. Cell
Krillin vs. 18
Piccolo vs. 17
Uub vs. Kid Buu
Ginyu vs. Recoome
Vegeta vs. 18
Trunks vs. Cell
Majin Buu vs. Kid Buu
Kid Goku vs. Yamcha

Glitch: Get to level 21:
Start a new story in Dragon Universe mode. Go to Kami's Lookout and level up. Save your game data and quit Dragon Universe mode. Then, start a new story in Dragon Universe mode and repeat this process until your Z fighter is at level 21.