The board game Confusion is excellent for game afternoons with exactly two players. And two players in my vicinity have been enjoying it recently! Confusion combines aspects of chess (each piece moves differently), checkers (the goal is the far side of the board), and Clue (there's lots of hidden information which you must query to investigate).
The setting: the Cold War. The pieces: Russian and US spies. The objective: obtain the briefcase of top secret intelligence, and sneak it to the opposite side of the board (while preventing your opponent from sneaking it to your side of the board). The gameplay: you can only see the names of your agents, while your opponent can see their move capabilities. The twist: one of your spies (labelled by '?') is a double agent, who obeys or disobeys you orders at the whim of your opponent. The trick: very good recordkeeping, just as with Clue.
The delight: when strategic use of your double-agent causes the opponent's entire strategy to collapse in a single turn!
My set of pieces had a misprint, and the friendly support at Stronghold Games promptly emailed me a replacement piece. Thanks!
This post's theme word is vitiate, "to impair or spoil the effectiveness of," or "to corrupt." My entire spy agency was vitiated when C turned out to be a Soviet double-agent!