I've got this monstrosity growing right next to my driveway. I'm fairly certain it's a Sunflower, probably Helianthus annuus... but I can't tell because it hasn't opened up just yet. Right now it's about 3 feet tall, and even though the head isn't opened it still tracks the sun during the day.

Various Helianthus species have enjoyed a rich history in Native American ethnobotany for pain relief, pulmonary agents and for smoking. Obviously, the seeds were (and are) used as a food. I'll keep you posted on the status of this volunteer.