Hercule: Use Piccolo's Dragon Universe (a second time). BEFORE fighting Buu, and AFTER the "event" at Central City, search the desert near Baba's Palace (if memory serves...to the right/East). After you talk to Hercule, go back to Central City and talk to Videl. After the conversation with Videl, Hercule will become unlocked.
Saibamen: In the Dragon Arena: Use a Level 10-20 Character, and battle opponents AT LEAST DOUBLE your own level. (Example: Levl 15 Gohan should battle a level 30 Anyone). Eventually, Nappa will "Suddenly Break In". Defeat Nappa, and the Saibamen will become unlocked.
Death is but a door, Time is just a window,...I'll be Back!!!!!