A Sunday Question: What Perennials Could You Not Garden Without?

Fall is fast approaching us here in Tennessee whether it feels like it or not (to me it feels like September) and I've started thinking about what to plant. Perennials are perfect for fall plantings since their roots grow slowly over the winter to become established root systems by spring. Then in spring the root systems are ready to go and the plant can send forth new fresh growth. If you plant the same kind of plant in spring it will have a slower growth process since it has to work hard on developing roots and making new foliage as well.

I've been collecting and adding new plants to our gardens as I can all year but I'd like to know what other gardeners view as "indispensable perennial plants." What perennials are the "must haves" in your garden? If you were starting a new garden which plant would you choose to begin with? I want to add some new things to my garden this fall and would like to hear some suggestions. Soooo....what should I plant?