A flashlight is a tool, not a weapon. Just like a hammer, wrench, or screwdriver. But ANYTHING can be used as a weapon. If you are defending yourself, then that implies that you were attacked. Because the attack was so sudden, you did not have time to retreat (if you live where that is a legal requirement before you can defend yourself). You instinctivly brought up your hands to defend yourself from this attack, while still holding your flashlight. It made contact with your attacker. That really made him mad. Maybe you remember him making additional threatening statements or becoming more agressive. Now you are in fear of your life or the lives of your family. Your attacker is now more determined than before. You strike or gouge your attacker until he is in a position that you can restrain him/retreat/get a better weapon to hold him at bay. If you do not have any warrants for your arrest, nor do you have a history of using your flashlight as an offensive weapon, I write up a report and list you as the victim and the other guy as the suspect. He goes to jail, and you go home.

This is not legal advise, just the way we look at things in my part of the world.