At close range (just a few feet) you can certainly "distract" a potential threat with a cheap D cell flashlight. For CQB applications 65-70 lumens is the industry standard for encandicent lights. Modern LED tactical lights can obviously provide considerably more than the standard and will temporally blind anyone unlucky enough to be in the way of the beam. Programble lights that feature a stobe mode are particularly effective.
US Night Vision Corporation