I'd have to go with Arundo donax 'Peppermint Stick' and Panicum virgatum 'Northwind.' 'Peppermint Stick' isn't as big as the species, and is really startling with it's variegated foliage. 'Northwind' is, by far, the most erect and upright Switch Grass, with it's blooms blended into the top of the foliage. Mine will hit 6' this year.

I'll second Donn's two suggestions and add Dallas blues panicum. Funny that I used to dislike all panicums, I thought of them as more of a
roadside and waste area weed than a garden plant.

I agree that any of the larger Panicums are absolutely stunning as specimens. Here in Portland, I really love Molinia 'Skyracer' & Stipa gigantea...talk about making a statement!