Fallout 3 has multiple endings, each dependent on a number of factors: karma, gender, whether the character lived or died, etc.

1. Gender
2. Karma
3. Character died or lived
4. Character sided or didn't side with President Eden

In an OXM interview with Bethesda's Todd Howard, it was revealed that there were over 200 possible endings. This was later clarified as actually being nine to 12 endings that play out in a final cinematic. Nuances of the cinematic are influenced by various factors, occurrences and decisions made throughout the game.Destructoid: Update: Fallout 3's 200 endings aren't really endings...

Multiple endings in videogames are nothing new. Nearly 50 different videogame franchises have played with the concept over the years. RPGs and Survival-Horror are the genres of games most likely to have multiple endings simply because of their complex design and character driven nature. However, puzzle games such as Bubble Bobble and Meteos have also featured multiple endings. Some game franchises, such as Silent Hill, have even become notorious for their unusual and in some cases humorous ending possibilities. The previous two games in the Fallout series both contained multiple endings, so it's no surprise that Fallout 3 is keeping up the tradition.Wikipedia: Multiple Endings: Videogames