Asters, autumn daisies in a wide range of colours from white, through all shades of pink and purple. Almost every garden has them and I know some gardens where they almost grow as weeds. They flower really late and give a strong splash of colour in September when most other flowers are beginning fade. They will tolerate light shade and bright sun and are relatively trouble free; what more could you want in an autumn flower.
We grow, and sell, Aster novi-belgii which is grown from seed (many cultivated varieties are sterile) and seems to be one of the most reliable for attracting bees as well as other pollinators. Right now (mid September) my asters are the buziest thing in the garden.