Just a poll I made out of curiosity.
I've unlocked all of (well, most of, but I know who's remaining) the characters in the latest installment "Dragonball Z Budokai Tenkaichi 3" and it still doesn't quite have ALL possible characters. What I list here are ideas of who I think would be good in the game.
Chichi - Well, in Super Dragonball Z, she was featured as a playable character. She used Nimbus to fly and Goku's Power Pole to attack (I think she used that instead of Ki energy.) It's true she's in BT3, but only her Dragonball self.
Puar/Oolong - Maybe they could just be involved as an appearance during special attacks. Dunno.
Crane Hermit - C'mon, I was expecting this one. He's the guy who trained Tien and Chiaotzu, and is also General Tao's brother.
General Red - Commander of the Red Ribbon army in Dragonball. Maybe he could just be like the General Red in Dragonball: Advanced Adventure and fight in a battle suit.
General Black - Worked under General Red. Same preference with a battle suit.
Major Metallitron - An android in the Red Ribbon army. Goku defeated him by shooting his head off with a Kamehameha.
Dr. Myuu - The creator of Baby. I'd love to see this guy work side by side with Dr. Gero.
HFIL Android 17 - The 17 made by Dr. Gero and Dr. Myuu which fuses with the earthly 17. I know he's technically the same character, but it'd be interesting if they made a separate character, with different/improved attacks and a different personality.
Kibito - All the time, the Supreme Kai has Kibitoshin as an optional character, but we never got Kibito separately.
Any others? Do comment on it.