High temperature PLA, I believe it is the best all around filament from the point of view of ease of printing and environmental impact, both in the outdoors environment and the indoors, there's no toxic fumes like with ABS for example.
The main problem with PLA is that it gets soft at around 60C, just 15 or 20 degrees higher glass transition temperature would be a huge improvement since those are not temperatures that can be found in a normal environment.