And do not skimp when purchasing a fire extinguisher. Your very life could depend on it, as well as that of your family. And that's not to mention how you will instantly become the most unpopular person on earth with your cohabitants and your neighbors if you burn the house down.
The next must-have item is a well-stocked first aid kit. At the very minimum, the kit should have adhesive bandages in a couple of sizes big enough to accommodate cuts and scrapes, some antibiotic ointment, disinfectant spray, sterile gauze pads, and adhesive tape. It's even better if you have some additional items such as ibuprofen, acetaminophen, aspirin, or some other analgesic for relieving pain, eye-wash, and a cold-pack for reducing swelling. Tweezers, scissors, burn cream, and sterile disposable gloves are also good items to have in the first aid kit. You'll usually find these latter items in the kits intended for industrial and corporate use. These kits can usually be mounted on the wall; next to the fire extinguisher is an ideal location in your garage.
Gloves will help keep you from getting cuts and scrapes, and also keep you from looking like a "grease monkey." Mechanics' gloves come in a variety of styles, and they're great for providing cushioning and protection for your hands when "wrenching" around. They offer a lot of tactile response (in plain English, you can still feel what you're touching), and they're good for doing heavy work (e.g., using wrenches, ratchets, sockets, air tools, hammers, and so forth).
Like many folks, I'm allergic to latex, so I prefer nitrile gloves for working on many projects in the garage. They come in various styles and thicknesses, and they're ideal when you have to be able to feel what you're doing. While they don't offer too much protection, they will keep you from getting "grease monkey" hands and ruining your manicure. Sold in boxes of 100, nitrile gloves are inexpensive and disposable, so you can toss them into the trash and use a fresh pair next time.
Protecting your eyes from injury is one of the most important things you can do when you're working in the garage. Think about it, you won't be doing any more work on your Corvette if you can't see what you're doing, right? Be sure to protect your eyes so you can continue to play in the garage. You have your choice of full-face shields, safety glasses, goggles, and even magnifier glasses, so you have lots of options for eye protection that's right for you and the task at hand.