Three suggestions that thrive on neglect and are tough,tough,tough:
1) Cosmos. I planted them in northern FL and here in central Ohio. In both places they grew like crazy.
2) Marigolds.
Don't turn up your nose. There are about a zillions varieties in all sizes, shapes and colors. There are marigolds with no (or almost none) scent, white marigolds (though they're actually a light yellow-ivory IMHO),and there are "mule" marigolds who spend all their time blooming since they can't make babies. Check out Burpee.com.
3) Zinnia. There are some lovely cadets of this family called Zinnia Augustiafolio (sp???). Instead of being a pom-pom head, they have flat pedals like daisies.
Nasturtiums are supposed to be very easy to grow but I nave never had any luck with them. :o(
If you are looking for perennials seriously consider OGR (old garden roses). Like the above 3 annuals these gals are tough and a lot hardier than their modern sisters.
Yellow marigolds are hearty plants but attract bees, found that out the hard way. Do the other colors attract bees?