This is St. John's Wort. 'Wort' is the Old English word for 'plant'. It has nothing to do with warts. The traditional pronunciation of St. John's Wort is Sinjun's wort.
It's Hypericum perforatum. The 'perforatum' refers to the tiny pores in the plant's leaves. That's how you can tell for sure that you're dealing with St. John's wort.
If you click the pic, you can better see the pores in the leaves. The sparkles on the edges are dew. I'm not sure what the dark spots are but they seem to be symmetrical, so I'm thinking it's just how the plant grew.
It is traditionally used to treat all sorts of things, most notably depression.