Cosmos bipinnatus is a very popular annual that has feathery, mid green foliage and a profusion of showy, daisy-like, open faced flowers that are held aloft on long stalks.
They are by their leggy nature, rather informal in style and work particularly well in cottage style gardens and big, mixed borders.
When they get to full height they may need some support, though if you plant them densely enough their own bulk can provide enough to keep them upright.
Cosmos are about as easy to grow as you'll get and they usually come in seed packs of mixed colours that add extra oomph to your mixed borders.