Here's a fun Easter Egg for System Shock 2:

When you first begin the game and exit the subway station, you'll be facing the UNN recruitment center. Go to the right and around the platform into the dark. Do a Thief-style "mantle" against the pipe-like thing there (i.e. jumping up and holding jump to pull yourself up to the platform above you.) Atop the pipe you'll find a basketball, which you can pick up (by centering it on the screen and right-clicking- you won't have the interface or targeting cursor to guide you, but it works anyway.) This is the only item you can take with you through training and to your eventual assignment on board the Von Braun. Hang on to that basketball for a while.

Later, on Deck 4, you'll be charged with the task of activating a transmitter, which happens to be inside a basketball court. Once you make your way there, get the ball through the hoop on the court for a secret message.