Wallpepper (a.k.a Goldmoss Stonecrop) is a multifaceted city plant. The plant can be found as small carpets between the pavement. The leaves are edible, but in large quantities they can cause stomach irritation. So it's better to cook them (especially if the plant is older). Perhaps the best way is to dry the leaves and then pulverize them so they can be used as a peppery seasoning.
EN: Wall pepper
LA: Sedum acre