There are a LOT of very good dual purpose breeds, everyone may answer differently. It depends on your needs, climate, and taste. For example, I live in a place that rarely ever gets hot or freezing cold, I want a good layer (preferably of eggs that aren't brown) but also a good meat bird and a broody bird, I don't want birds from hatchery/production stock, and I want something different - So, my choices are breeds like Araucanas, French Marans, and Brahmas. Though Brahmas do lay brown eggs, they make up for it in other areas such as new rare colors, beautiful bodies, huge size, and wonderful temperament.
My favorite thing to do with dual purpose poultry though is cross-breeding, honestly. There are some ideas out there that just don't exist, and so I work to create them. (meaty, showy white egg layer, gaudy colored and meaty bodied dark olive layer)