These are some of my favorites for sunny area and very easy to grow. Some can be in partial shade:

Rudbeckia fulgida var. fulgida
Rudbeckia 'Goldsturm'
Miscanthus sinensis 'Morning Light'
Liatris 'Kobold'
Salvia (Many vaireties)
Asters (My favorites are Aster frikartii 'Monch' & 'Flora's Delight')
Clematis
Perovskia (Russian sage)
Echinacea purpura
Alchemilla mollis
Achillea 'Coronation Gold'
Anthemis kelwayii
Sedum 'Autumn Joy'

Don't forget to plant some shrubs to give structure and long interest:

Lilac
Viburnum
Hydrangea arborescence 'Annabelle'
Cornus alba sibirica, Cornus alba 'Elegantissima' or 'Ivory Halo', Cornus sanguinea 'Winter Flame'
Caryopteris
Dwarf conifers or full size if you have room.

The choice is endless. Oh, don't forget tucking in bulbs in any space you have left. Your garden to have a very long blooming season.

Happy gardening. :-)

The words "city" and "ivy" make me wonder if you're contending with dense building shade for at least a good part of the year. If you are, things like heuchera, hosta, anemone, cimicifuga, aconitum and ligularia might be up your alley. Peonies are super-easy too, but they'll only bloom well if you have decent sun. What are your conditions? Do you have trees? Tall buildings nearby, especially to your south? Limited space? None of the above? Nice soil? Sand? Clay? It'll be easier to make good suggestions if we know.

I like all of the perennials mentioned and they cause me very few problems...I think the most indestructible has to be the Sedum Autumn Joy...and it's really pretty for a long period too...
Jean

Thanks everyone for the many suggestions.
I already have four peonies plants that
bloom beautifully every year.They get a full
dose of afternoon sun.I can see a few little red buds
coming out of the ground already.
I am in the city,but I still get a half day of full sun
in the yard.The ground here is pretty good too.
I am surprised with the all the varieties
that survive in our area.The Sedum Autumn Joy may be
just what I'm looking for;Pretty... And Indestructable!
Thanks again,and any more advice is welcome.