Unreal Tournament
Dreamcast

Level Skip:

Pause the game and press Up, Down, Left, Right, Right, Left.

Invincibility:

Pause the game and press Left, Left, Right, Right, Down, Up.

Max Ammo:

Pause the game and press Left, Right, Left, Right, Right, Left.

Refill Health:

During the game, press pause and press, Down, Down, Down, Left, Up, Right.