Doom 64
Sent in by Jesse O'Clock
After destroying the head demon, (although they never
tell you who it is) the space marine is standing defiantly
in "outer darkness" that he's destroyed. And a message comes
up that is more or less like this. "I've finally done it! I've
killed the head demon and ended my nightmare!" Then he
decides to stay in "outer darkness" forever to make sure
that no demons will ever rise again. The it shows a screen
with a zombie on it, and when you press a button, it blows
up, and then all the monsters come on the screen one by
one, and you can keep on killing them!