Ivy-leaved toadflax, aka Kenilworth Ivy (Cymbalaria muralis/Linaria cymbalaria) is one of these wild plants that is rarely considered a weed. Why? Well, in the company of stinging nettle and cleavers, this one is a beauty contest winner.
But its value is beyond ornamental; it's a wild edible as well. According to old herbal books, ivy-leaved toadflax has anti-scorbutic properties, wich means it has a high vitamin C content. We use the flowers and leaves mainly in salads. You can harvest for a long period of time, and its taste is a bit acrid and pungent like cress.
It's a flowering plant native to Mediterranean Europe and widely naturalised elsewhere. It commonly grows in rock and wall crevices (hence the French name 'ruine-de-Rome'), and along footpaths. We have it in our yard, growing on our old garden wall. Which is nice, because the plants that grow in the soil are challenged in our garden, given the fact that we were adopted by an elderly free range rabbit, who loves wild edibles as much as we do :)