This post is a continuation of the previous discussions on BCD's in the sense that I will be discussing items that you could carry in the BCD pockets.
Signaling devices: It is a good idea for every diver to carry at least one signaling device. Some signaling devices that divers carry are whistles, mirrors, "safety sausage", lights, air horns, tank bangers and so on. Signaling devices can used to alert a boat at the surface to pick you up if you happen to drift away from the boat or surface a distance away from where the boat is. A safety sausage is an inflatable device that you can inflate using a regulator. They are typically around 4 to 6 feet tall and are either bright yellow, red or a marmalade color. At night you use your dive light and illuminate the inside of the safety sausage.
Knives, EMT shears: There are many different kinds of dive knives available. The type that I would recommend are made from titanium and do not corrode due to salt water immersion. Knives come in various styles. Some have rounded blade tips and some have sharp blade tips. It is a personal choice, but most people recommend a rounded tip on the blade to prevent accidental punctures of your gear etc. Some people have the mistaken idea that a knife can be used to fend off an attack by a marine animal and therefore choose a sharp tipped blade. The primary purpose of a dive knife is to be able to free yourself from underwater entanglements like fishing line, rope, etc. An alternative style of knife is a small knife that is sold with the BCD. The knife fits into a sheath in the shoulder harness. The advantage of these BCD included knives is that they are small, easy to carry and out of the way.
Some divers (myself included) like to carry a knife and a pair of EMT shears. The shears work differently to a knife in that you can easily cut through something using only one hand. Personally I like to carry my knife in my BCD pocket and my shears on the front of my BCD close to my left shoulder. The advantage of carrying two cutting devices in different places is that you can always reach one of them if you become stuck somewhere.
Some divers like to carry their knives on their left or right calves. I don't have a problem with this except that dive knives are the one article that is most often lost by divers, because if you are not careful, the blade can easily detach itself from the sheath and you will have to stop in at the local dive store to purchase a brand new shiny knife.