Soul Calibur II
Speak during load screen:
Press L1, R1, or X while a stage is loading.
Press Guard when selecting a character.
Finish chapter 2 in Weapon Master mode.
Beat the first mission in chapter 3 in Weapon Master mode.
Finish chapter 3 in Weapon Master mode.
Finish chapter 4 in Weapon Master mode.
Unlock Seung Mina:
Partway through chapter 6 in Weapon Master mode, you'll fight Seung Mina. Beat her to unlock her.
Beat Weapon Master mode once. Next, complete crystal mine in chapter 8 in both normal and extra mission. That will lead to subchapter 3. You'll see a second misssion called Castle of the Damned. Beat it in Normal and Extra to unlock Assassin in the Practices and the Two-Player modes, but no Arcade modes.
Beat Weapon Master mode once. Now play subchapter 1 again, the dungeon level with lots of beserkers. Beat the Boss to unlock Beserker in all modes except Weapon Master.
Beat sub chapter 2 in Weapon Master mode. To open this up, you must complete chapter 4 in Normal and Extra and reach level 72. Lizardman is only playable in the Two-Player modes and Practice.
Finish the southern-most mission of chapter 3 in Weapon Master mode. A road will appear. Take it to find a shop selling the martial arts demos.
Extra Arcade mode:
Beat Arcade mode with any character.
Extra Vs. mode:
Beat Extra Arcade mode with any character.
Extra Survival mode:
Beat Survival mode with at least ten wins.
Extra Practice mode:
Beat Weapon Master mode with any character.
Extra Vs. Team Battle mode:
Beat Extra Team Battle mode.
Thanks to Revolution readers Martin Brodeur, Sean, Silver Phantom, Ralph Wiggum and Lissette!