Diplomacy is a strategic world war one game that is playable as a board game or as a play by email game or as a video game (although the last variant kind of sucks).
This is one of my favorite strategy board games.
Since it is really best when played with the full seven players and takes at least four hours to play, it is difficult to organize in person games.
Play by email versions of the game are also fun. But they have a very different dynamic and feel then an in person game does.