I'm planning on creating an iPhone game titled "Guess Who!". I know there is already a board game with the same title (linked here) so I'm wondering it is legal for me to use this title for my game. Will the game get pulled off of the App Store if I use it? Thanks in advance.
You'll best find this answer by querying Apple and places where Apple app developers post. Well, that and contact a legal professional. The question is really quite independent of whether it's a game, a productivity app, or anything else.
That said, the fact that your game and a different game (even if it's a board game) have the same name is likely to create an issue, simply because consumers may confuse your game with the board game. Does Apple care about this? I don't know. But does the maker of the original game care? That's the big question (IMO). If they don't like it, they've got a fairly legitimate argument (in my mind) that your game's name creates confusion about their game, and I assume they have already legally protected their name in some way.
Best advice? Just pick a new name. Or be ready to argue that, "Guess Who!" is sufficiently generic enough that many games could have that name.
From personal experience, no it is not legal. Never ever use the name of a company or product in your product name. Examples of bad names:
On the Apple market, your game most likely won't pass review because they have a descent legal department and they will force you to change your name unless you can prove you have rights to Guess Who.
If you were actually published then the entity that owns rights to Guess Who would have the option of filing a DMCA takedown request on your app. Your app would then be shutdown permanently pending a counterfiling by yourself.
See the pretty info-graphic here for the remainder of the process: http://blog.nexcess.net/2012/02/22/dmca-process-infographic-flowchart/
Simply put ; that depends on what rights and trademarks have been registered for that other game's name.
For example, not too long ago, Bethesda sued Mojang becuase they were about to launch a game called "scrolls", and Bethesda's lawyers sued Mojang becuase they worried about their trademarks on "The Elder Scrolls".
So even a name that sounds like a famous game name might get you into trouble.