5. Duke Nukem Finds The Launch Pad
Duke Nukem 3D was many things, subtle not being one of them. Racing down a drain of toxic sludge during the fourth level of L.A. Meltdown entitled Toxic Dump (how appropriate), there is a room off to the left side before the end. Skip this room and you will immediately find the end of the level, but hop out of the muck into the room on the left and aliens guarding a super computer will greet you. Kill the aliens easily and approach the computer. As you draw close a deep, evil voice will announce "Secret Level." Like I said, not so subtle. Ending the level will take Duke to the Launch Facility. There he discovers more alien bad dudes attempting to use one of Earth's rocket ships for their own purposes. Duke puts an end to it quickly by destroying the rocket.