Purslane
This plant has rounded, succulent, leaves and a reddish stem and grows everywhere, so it's very likely that you'll find a purslane plant somewhere in your neighborhood. Notoriously difficult to kill as a weed, purslane is probably better suited to your dinner plate anyway. It's loaded with antioxidant vitamins like vitamins A and C, and also contains healthy omega-3 fatty acids. You can eat the stems and leaves fresh—try them in salads or sandwiches—or use them in soups or in recipes that call for spinach (they’re related and have a similar taste).
Photo: (cc) pellaea/flickr