My top five annual flowers - #3, Verbena bonariensis

Yes, the name is a mouthful, but this is a great little plant.  This tough species of Verbena is such a reliable self-seeder that you you plant one Verbena bonariensis, you may never have to plant another. It also winters over given just a bit of shelter from cold hard winds.
And yet it  never seems invasive, because the neat early rosettes of foliage can be easily pulled from places you don't want this willowy, purple flowered butterfly magnet to grow.... though I 'm not sure where you would not want it!
Here's a big patch of bonariensis I let fill in after I pulled my garlic plants in July. The foliage is still clean and green and new flower shoots are sent up every day:

In other parts of the garden I have left just one plant, and I really enjoy the effect of the tall flowers coming up through the vegetable plants, in this case a trellis of Rattlesnake pole beans.

Verbena bonariensis has several characteristics that keep it from being the perfect kitchen garden annual; it is not fragrant nor edible, and as a cut flower tends to shed a lot.
Bur right now, when so many other garden flowers are tired and ragged, the Verbena stands tall and bright.