Toothache plant, Peek-A-Poo plant (Spilanthes oleracea).
This annual is used in salads because of it's pepper like flavor, and is also chewed for toothache because of it's anesthetic properties, this is how it gets it's common name of Toothache Plant. It is a native to South America and is only hardy in warmer climates. Spilanthes oleracea has flowers with round yellow balls and a red "eye" on top. In addition to the unique flowers, Toothache plant has attractive bronzy, dark green foliage which is edible.
If you want more information about this flower, just search the plant's Latin (botanical) name on Google: