Giant hyssop will continue to spread a bit year after year, which can be helpful in filling in a large area over time.
Coneflowers, also known as echinacea, are such easy-growers they may even reseed to spread themselves.
Hardy across most zones and a pollinator favorite, sedum has not only showy flowers, but showy foliage, too.
Going up with interest is the advantage of blazing star/liatrus--that, and the hordes of butterflies, bees, and hummingbirds that will be visiting.
Low-growing dianthus, or "Pinks" as they are often called, will treat you year after year with next to no care.
Probably one of the biggest reasons lilies are such a timeless classic is their easy care.
Poor ground and growing conditions are no match for easy-care hens and chicks. They'll literally grow in the rocks!
Hibiscus has something of a reputation for being tricky to grow, but not if you have the right hardy variety.
There are many more color varieties of yarrow than many people know of. Several colors can exist on one plant.