The first touring / wagon car that was cool for me, was the Audi RS2 Avant. A joint-venture project by Audi and Porsche, it is very clear from the start what they were aiming for.
I'd say the first estate / wagon that captured my attention would've been the Volvo 850, the shape was so much nicer than the equivalent 850 sedan, and they went completely mental and decided to use them to compete in the BTCC!!! I've never fancied a wagon so much. Obviously the Audi RS2 was also a landmark car in that regards, the subtle hint of Porsche add-ons were just prefect, the mirrors, the wheels, brakes, front indicators, etc but the 850 was far more accessible to the masses.