Double Dragon
Double Dragon -- Template:AL-Melbourne House
When the title screen pops up, type in the followings:
LEVEL ONE PLEASE (start on level one) LEVEL TWO PLEASE (start on level two) LEVEL THREE PLEASE (start on level three) LEVEL FOUR PLEASE (start on level four) THE LAST LEVEL PLEASE (start on last level)
GIVE ME MORE HEALTH PLEASE (lots of energy!) I DO NOT WANT TO DIE (invincibility!).
Also, type Neil Harding in the high-score list and something funny happens...
And finally: start a 2-player game and hold down both fire buttons, then hit Esc like crazy until the credits go bonkers and you get infinite lives.
The last two need someone to test them and write up what happens.