Can someone please tell me what kind of flower this is?
This is Monarda citriodora or "Lemon Bee Balm".
Monarda citriodora is a species of flowering plant in the mint family, Lamiaceae, that is native much of the United States and Mexico. Common names include lemon beebalm, lemon mint (this may also apply to Melissa officinalis) and purple horsemint. When crushed, the leaves emit an odor reminiscent of lemons. This odor is sometimes described as more resembling oregano, especially late in the season. Its purple flowers are highly attractive to butterflies, bees and hummingbirds.
It is an annual plant although it readily reseeds itself once established.
More information: http://www.wildflower.org/plants/result.php?id_plant=MOCI