Medal of Honor: Allied Assult.
You blow up a mustard factory, and escape on the train and all that happens is. ..
Black screen: The End.
. . .
I mean, come off it! Oh well, it was a great game.

I've seen worse endings, but I have to think about them. It's been a while since I played a game that had an ending so crap that it was rememberable for it's crappiness.
- DH