Check this page out... totally amazing... the guy did, without using the console, manage to do several things in the game. He saved some scientists that should die (scripted), and almost saved others. He even managed to get up close to the GMan - tried killing him in many ways but failed of course. Very, very inventive and worth checking out.
http://www.colinfahey.com/apr2002_ofsave/apr2002_ofsave.htm
http://www.colinfahey.com/apr2002_ofsave/apr2002_ofsave.htm