Somehow Alyssum totally escapes being eaten by my Slug Army.
That was how I found them: I planted a mix with dozens of flowers in it. The only two that were not eaten were Alyssum and Siberian Wallflower.
Siberian Wallflower (Erysimum marshallii)
Zinnias seem survive with only a few bites, but I've started them indoors, and only put them out when pretty big. That isn't necessary with Zinnias, but it does frustrate the slugs.