Church (and Giant Chickens) of Burgundy
A first play of a 'classic' game which everyone assumes I knew - Castles of Burgundy. None of us playing had played it before (which refutes the classic status a touch) and needed a restart after we'd found we'd got a few rules wrong. Not the clearest of rule books.
However, into the game proper and I can see why it's popular. Multiple tricky decisions of the best use of limited semi-random choices.