These are games that are not nesecerily restricted to 2 players they might not even play best with 2 players, but they play very well as a 2 player game. Lots of games are designed for 4 players and are unbalanced with just 2, or certain mechanics just don't work aswell, if you are only gaming with 1 other person check out these titles.
Lords of Waterdeep - Almost like an entirely different game, if you think LoW is just a intro to worker placements, a cash grab or a theme pasted quickly onto a euro, try LoW with just 2 players. Even if you love the game with more players, try it with 2. It is a very very strategic worker placement, my only issue is that it can either feel too solitaire or too "luck" based because of mandatory quests.
Safranito - Want something you can play to relax? Almost zen like game play, a 2 player game of Safranito feels less like a bustling market where you must fight the crowd to buy your ingredients and more of a concentration get in the zone home garden in the back of your house where you grow everything you need for your recipe.
Call of C'thulhu - Limited to 2 players, this is my recommendation if you like: elegant game play, lovecraft, scary horror monsters, mystery, deck construction, backstory / lore.
Warhammer Invasion - Looking for a fast paced jump right into battle with your opponent game? Warhammer Invasion requires you to balance your kingdom while setting your opponent's ablaze. Made for two players this is a conflict driven game and is great if you just want to beat the snot out of a friend.
Android Netrunner - Is Netrunner all its cracked up to be, I mean how has it locked down the hotness section on Board Game Geek since its release basically never losing a top 3 position? Well I am here to help you make that decision for yourself. First I will give a brief overview of how the game is played, then I will compare it to the other LCGs I have played and why it is such a must have 2 player game.
Army vs Aliens