Flashlights are normally used in Colonial and Earth society as a means of lighting dark places. It was developed to replace the candle and torch as a means of portable light. On Ragnar Anchorage, Commander William Adama infamously used a flashlight to beat Leoben Conoy to death after it was discovered that he was a Humano-Cylon agent.
Also See:
Flashlight at Wikipedia
Flashlight at The TV IV