muttly13: If card games count, Munchkin and all expansions.
Actually, I would recommend against this, unless you play with the right "crowd". Munchkin has a tendency of dragging on for too long, as it is too easy to prevent a player nearing level 10 from reaching that level, unless that player gets lucky, and it also has an inherent "meanness" factor that makes some people uneasy. And finally, it is very joke dependent, so unless you get pen & paper RPG jokes+the subject of the particular Munchkin version, it might not be all that fun.
Though if you play with the right kind of people, it can be quite fun.
Also, far too many monopoly recommendations has been spotted in this thread. Monopoly is an old game, and it has aged really poorly. If you are not familiar with modern board games, then you might not be able to spot the obvious flaws in it (and the same is true for Risk), but for anyone who has some experience with modern games, the huge flaws of Monopoly just becomes painful. I would go so far as to say that by today's standards Monopoly is an objectively bad game.
And here is a good video to watch on the subject:
http://www.youtube.com/watch?v=-4nofYNC67s&feature=relmfu