Make sure you have the right extinguisher for the type of fire you have to put out. Failure to due so will result in injury or death.
The most common 4 types are A, B, C, and K. In the home, vehicle, and radio shack a combination ABC extinguisher meets most if not all your needs. I have rarely seen D type extinguishers. Combustible metals are usually seen in labs and manufacturing. The K type extinguisher is required in most commercial kitchens by the Fire Marshal or Authority Having Jurisdiction. They work very well when
cooking oil or grease are on fire.
It is also not uncommon to see water fire extinguishers. DO NOT use water on electrical or grease/oil fires! Water on a grease/oil fire will flare up and very rapidly spread. Use on an electrical fire will shock or electrocute you as your attempting to put out the fire. Some water extinguishers that have mist nozzles attached, are rated for class C (Electrical fires). I personally do not trust that and will stick with the ABC in most cases. With Electrical fires always turn off power or unplug equipment before attempting to put out fire.
There are many more specialty extinguishers for a variety of different situations. We will save those for another day. Stay safe!