1. Jack and Jack Stands
If you're going to be working under your vehicle, you'll need access to it. A quality jack and jack stands can help you safely lift and support your vehicle for work under the vehicle where some of those repairs may take place.
Your vehicle may have come with a jack, but I recommend purchasing a higher quality set." recommend a quality jack and jack stands instead of the jacks that may be found in your vehicle. These higher-quality jacks and jack stands tend to be more sturdy and safer to use.
2. Lug Wrench
A lot of automotive work takes place behind the wheels and tires. For example, you'll need to remove the wheels to gain access to the brakes and suspension. A good lug wrench can make easy work of this. This is a tool that may already be in your vehicle if it's equipped with a spare tire.
3. Socket Set
This set of many tools is useful to remove or tighten the various sizes of nuts and bolts on a vehicle. If you're going to be doing service work on your vehicle, you'll likely need a socket set with a variety of sizes. Socket sets usually come with a ratcheting handle which allows for reversing in confined spaces without removing the socket from the head of the nut or bolt. I recommend sets in 1/4-inch, 3/8-inch, and 1/2-inch sizes with extensions. That way you should be able to tackle almost anything comes your way.
4. Wrench Set
Once again, this is technically many tools, but like the socket set, I believe it's a necessity for working on your vehicle. Ratchets and sockets may not always do the trick. Sometimes access is tight (especially in the engine compartment) and the only tool you can use is a wrench. It's good to have a variety of sizes and styles on hand for those hard-to-reach places.
I know, I keep sneaking in extra tools into this list. Believe me, it's for your own good. Nothing is more frustrating than not being able to do a repair because you don't have the right tool. The more tools you have access to, the better.
At the very least, I think vehicle owners should have a Phillips- and flat-head screwdriver. Having both of these in a variety of sizes is even better. You may also consider some torx (or star-head) screwdrivers thrown in for good measure.
6. Inspection Light
So much of diagnosis is dependent on observation. Many of the areas of your vehicle that require inspection are often poorly lit (or not lit at all). A good inspection light is great to have in these situations. After all, you need to see what you're doing. You might also consider a light that can be mounted to your head for convenient, hands-free use.
7. OBD II Code Reader
All vehicles since 1996 have used the On Board Diagnostics (OBD II) electronic interface to help aid in the diagnosis of your vehicle. If your check engine light comes on, or if you've failed an emissions test, an OBD II device is very handy to have. They're also fairly inexpensive, and some can even work with your smartphone.