The tools necessary for drywalling a room are, for the most part, pretty basic. You probably have most of what you will need lying about your garage or perhaps neatly tucked away in your tool box.
For cutting drywall, you need only two items, a utility knife and a keyhole saw. The utility knife should be sharp, and I like to have the handle brightly colored so it is easy to find among the debris that seems to accumulate when doing drywall. The keyhole saw should be short and sturdy. An experienced drywaller can even jam it through drywall without drilling a hole. You might want a drill to make the initial hole for your keyhole saw.
A wedge of some kind is handy for holding up or sliding drywall edge over the floor. You can even use a scrap piece of drywall for this purpose. Depending on if you are nailing or screwing your drywall, you will need a hammer or an electric drill (cordless or not). These are the simple tools for what is often called "hanging" wallboard.
For mudding the walls, you will want to have trowels or joint-knives of various sizes (a six and ten-incher at minimum), a corner trowel is handy, but not absolutely necessary. Also, a hod of sorts for carrying around extra plaster will prove its value.
For the final step, sanding, a special type of paper is best. It is a mesh that looks like a very gritty screen. The holes let out the extraordinary amount of dust that is generated. You may choose an electric sander or sand by hand. My experience is that an electric sander creates dust so fast, that I cannot keep up with it, wiping it off my goggles every few minutes. If you have put the mud on properly, sanding should not be too difficult even by hand.
Just for safety's sake, you should wear goggles and a hardhat while doing drywall. Work gloves are also handy to have when handling large sheets of wallboard. Use a face mask when sanding.