Hi Mezavictor,
Your picture isn't really close enough for me to be sure and I don't know where you are located, but I suspect your plant is Lippia citriodora aka Aloysia triphylla aka lemon verbena.* Is this it?
http://www.plantcare.com/encyclopedi...rush-2305.aspx
http://www.littleherbhouse.com/Aloysia-triphylla1.gif
http://petalsfromthepast.com/catalog...%20Verbena.JPG
I have it in my garden and it will seed around the garden if you let it set seeds.
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.