hens & chicks come to mind, what about sturdy sedums. In my experience I've made a row of stones where the water hits the soil and plant in front of the stones most anything.

I have strawberries in the same situation, and they love the extra water. They are interplanted with chives to deter pests.

Thanks for the responses!
I need something a little bushier and with a little more height than sedum or "groundcover" to break up the line between the lawn and the tall, blank garage wall. Plus a quantity of Sedum or hens/chicks adequate to fill an 18"x 30' space would go into the hundred$.
I can't get Strawberries to thrive for some reason . . . I can definitely get chives to thrive, but . . . it wouldn't look s great before a downpour, and would look horrible (all layed down etc.) after getting battered.
The things I have on hand in quantity are Hosta,Painter's pallet, Kerria Japonica, gooseberries . . .any thoughts as to which of these could best handle a battering?

What about something with a more woody support structure? Epimedium comes to mind - nice spring flowers. They are pretty indestructable. Some nice leaf detail too.

Astilbe love wet feet, but they get a bit tired looking in Ohio heat - they might work better in Chicago. The bigger old fashioned kind might work best.

Depending on your foot path, you might try a small shrub/bush. I personally hate boxwoods, but nothing kills them. You might even get away with one of the hydrangeas that grow from the ground each year, but it would be a pain to keep it within your boundaries.

Good luck!