Polymaker Fiberon PA612-CF15 Carbon Fiber Nylon Filament Black 0.5kg, Fiberon PA612-CF15 Strong & Low Moisture Sensitive Nylon 3D Printing Filament

The most engineering-minded consumer brand in this space. Polylite is their everyday PLA, PolyMax adds impact resistance, and PolyWood nails the timber look. They publish data sheets and actually explain what's in their formulations.