There is a character cast of at least 39 in Dragon Ball Z: Attack of the Saiyans (entitled “Dragon Ball Kai: Saiyan Invasion” in Japanese).
The game is a turn-based RPG based on the Dragon Ball Z anime for the DS. It is developed by Monolith Soft (Xenosaga, Baten Kaitos, Disaster: Say of Crisis) and published by Namco Bandai.
Storywise, the game spans through the Piccolo Jr. Saga in Dragon Ball, up to the Saiyan Saga in Dragon Ball Z. It will be released in America and Australia this November 2009.
Here is a list of the characters in the game:
1. Bora
2. Broly (Secret Boss)
3. Bubbles
4. Bulma
5. Chaozu
6. Chi Chi
7. Farmer
8. Fortuneteller Baba
9. General Tao
10. Ghost Usher
11. Gohan
12. Goku
13. Great Ape Vegeta
14. Hero
15. Icarus (Possibly)
16. Jackie Chun
17. Kami
18. King Chappa
19. King Kai
20. King Yemma
21. Korin
22. Krillin
23. Launch
24. Master Roshi
25. Monster Carrot
26. Mr. Popo
27. Nappa
28. Ox King
29. Piccolo
30. Puar
31. Raditz
32. Saibaman
33. Tien Shinhan
34. Turtle
35. Upa
36. Vegeta
37. World Martial Arts Tournament announcer
38. Yajirobe
39. Yamcha
Here is a Japanese video showing off some of the characters in the game.
And here is a gameplay trailer!