For marathon or ultra running I use Brooks Racer ST 3 (the latest model is 4). Can be used on any road and maybe on some easier trails as well.
A slightly lighter and narrower racing flat for track intervals and all fast road running up to marathons: Adidas Adizero Adios.
When I want to run semi-barefoot to strengthen my feet, and also when I walk or jog in a city (shopping etc) Feelmax Niesa is my choice. It's generally good for all traveling also.
Finally for challenging trail running I use the North Face Rucky Chucky. Yes they are a bit heavier, but in extreme conditions safety is more important than speed.