Battlestar Galactica

Starbuck and Apollo as wingmen:
Press Down, Down, Left, Down, Down, Up, Right, Right at the "Extras" menu.
The Cylon will saying "By your command", if you entered correctly.

Unlimited missiles: Finish mission 2 in the expert mode
Invincibility: Finish mission 9 in the expert mode
All wingmen: Finish the game in the normal or expert mode

Unlock Bonus Mini Series Content
During the game hit Left, Up, Left, Left, Down, Left, Up, Down, Up, Up, Down,
Down, Right, Up, Right, Down.

Go to the extras menu an press the following button combinations:

Unlock picture #1: Down, Down, Down, Down, Left, Left, Left, Left.
Unlock picture #2: Left, Up, Left, Left, Down, Left, Up, Down.
Unlock picture #3: Right, Right, Right, Right, Down, Down, Left, Left.
Unlock picture #4: Right, Right, Up, Up, Left, Left, Up, Up.
Unlock picture #5: Up, Left, Up, Right, Up, Left, Up, Right.
Unlock picture #6: Up, Up, Down, Down, Right, Up, Right, Down.
Unlock picture #7: Up, Up, Up, Down, Down, Down, Left, Right