Tire Irons come in Standard and Metric sizes, it's helpful to have both equipped for both applications to keep from stripping lug nuts. With the advancement of modern technology, cordless impact guns have become popular. Even if you keep motorized tools like a cordless impact, it's a good idea to keep a tire iron as back up just in case the batteries aren't charged or the torque capacity isn't enough.
Another backup tool to keep in mind would be a standard breaker bar and socket set for lugs that are too tight for other tools to remove. Often times shops that install tires use pneumatic tools that can tighten the lugnuts down to a point that can make them very difficult to remove.
