hm...the game Portal was based on...

[Zovistograt]

I just found this :O

http://www.answers.com/topic/narbacular-drop

obviously old, and it's not as professional or polished as Portal, but...it's what Portal is somewhat of a sequel to so that's pretty cool.  It was also made by DigiPen students :D

[StateAardvark]

*inb4nothinghappens*

[NINTENDO_PAWNAGE_RAWK]

*Loves End Credit Song*

Spoiler if you have not finished the game.

http://www.youtube.com/watch?v=RthZgszykLs

[Ares300]

I heard that you MIGHT get the portal gun in Half-Life 2: Episode 3. Maybe even get a slice of cake.