Which games are secretly better at 2 players than at their "ideal" player count?

My partner and I play way more 2-player than group games now, and some of our favourites are games where the box says 3-5 but the 2-player version is tighter and more strategic. Others completely fall apart without a third person to kingmake. What games surprised you at 2, and which ones should never be played as a duo?