In previous questions many users asked whether or not an athlete can be used in a game. Yet the answer was no due to multiple copyright their images and names had. However anyone can use a politician's name and physical appearance due to the fact that they are "public figures" (example: Obama). In this case, I want to use famous game developers such as Kojima and Gabe Newell in a game. Am I allowed to use them? or should I make references to them using distinct names (I.E. Lord Gaben). How can I find out whether or not a person is a "public figure" and if their appearance/name is protected?.
Generally speaking, personality rights prevent you from using another's name or likeness without permission.
There are exceptions, especially depending on your jurisdiction. The United States is particularly involved, as I recall, because many states have laws concerning publicity which may all differ slightly. It is best to talk with a lawyer familiar in the matter about your specific intent.
To determine who should be contacted to negotiate for a license to somebody's personality rights you should also consult a lawyer.
The consequences of using a celebrity likeness can lead to severe legal repercussions as Todd McFarlane could tell you.
In the Spawn comic book series, Todd McFarlane created a mob enforcer character named Antonio "Tony Twist" Twistelli, who McFarlane acknowledged was named after Tony Twist. Twist won a $15 million verdict in 2004 when a St. Louis, Missouri jury found Todd McFarlane Productions had profited from Twist's likeness. The verdict was upheld after two appeals in June 2006. In 2007, Twist and McFarlane settled the lawsuit out of court for $5 million.
Long story short - generally you cannot use celebrity likenesses for living figures. For dead, historical personages it's another story but still not 100% safe.
For living figures you can pretty much forget it. You can claim parody but only if the whole game is obvious parody and it helps a great deal if you are known as a comedic personality of some kind. Even so, nothing stops you from being sued on those grounds even if you are in the right and the legal bills could be quite expensive.
For historical figures you are generally OK but there still may be restrictions so it could be worth speaking to a lawyer, and anything touching on properties or companies that they may have been involved with is completely unprotected.