I'm in the common situation of liking board games, not having the time and energy to join a game group, and playing mostly with my wife. There are a large number of great games made for two players, but usually they are smaller in scope than games that can accommodate more players.

This list is of games that are playable by 2 or more, but are worth purchasing solely to play as a two player game. If it does not "officially" support 2, but has a two player variant that makes it a worthwhile purchase, that is just fine. I don't want any games that only support two on the list, as those are obviously worth purchasing just for two players.

To be clear, for purposes of this list, it does not matter how the game plays with more than two players. It does not matter how many players it is "best" with. What matters is whether the game is worth purchasing only to be played with two players.

Other geeklists that are similar are here, but none are as comprehensive as this aims to be:

http://boardgamegeek.com/geeklist/2816
http://boardgamegeek.com/geeklist/984
http://www.boardgamegeek.com/geeklist/14971

A particularly good list is here, with much more in depth commentary:

http://www.boardgamegeek.com/geeklist/14040

A geeklist with 2-player variants is here, which includes some of the variants discussed below:

http://www.boardgamegeek.com/geeklist/15749

Feel free to comment or add more games. I've added games that I think are worth purchasing just for two, and games that I haven't played, but appear from forum comments and other geeklists to be worthwhile.