Ever on the look out for unusual plants, I luckily happened on an out of season plant sale several years ago at a nursery that unfortunately sells only to landscapers now and was able to pick up some Rudbeckia maxima the giant coneflower for 50 cents each. There were about 5 left over by the time I got there and was about to buy them all but my dad who was along for the trip said "why are you buying those ugly, half dead things". So I bought only two which was a mistake for they turned out to be quite a wonderful tall element in a garden - I should never listen to someone else about plant choices/quantity and later since my wife and I liked it so much we bought more at another nursery for $12 each! My wife and I liked the unusual whitish green leaves and the 6-7 feet tall flower spike. It needs full sun though and unfortunately we don't have very much unshaded garden space anymore so the coneflower tends to fall over. It doesn't produce many blooms but that's ok as the flower is carried aloft proudly on the tall stem like a flag on a pole.
The goldfinches also like the seed so that's another bonus. Here's a website that gives a good description of the plant.