I refer to any flashlight using a high-output bulb or LED (minimum 40+ lumens) that runs off of CR123A or equivalent rechargeable batteries as a tactical light. Most of these lights have a click on, click off or twist on switch fitted into the tailcap. For comparison, a Mini Maglite (2 AA batteries) has no switch, but you must twist the bezel to turn it on. This takes time and fine motor control that may not be afforded in a given situation - and you get much worse light output for your trouble.
You may want to head over to http://www.flashlightreviews.com/ . Read through the reviews of the 3 watt Luxeon or Cree lights, or search for reviews of lights from Mag Instruments and Surefire for good examples of general use lights vs. tactical lights.