For blinding someone at short distances, 60-65 lumens is considered the minimum. With 100-200 or so, you get a pretty long throw for checking your surroundings outdoors or lighting up half a room. I'm not an expert, but I have 2 Surefires and one Digilight as well as some $2 utility lights and an old plastic 2D battery.
A 2 or 3 battery Surefire or Streamlight would be a decent choice.