I-40 does pass through the Petrified Forest in Arizona, which is something you should see. It's a lovely drive through the desert with frequent stops along the way having short hikes to see interesting and beautiful examples of petrified specimens.
There is also a large knife store near Holbrook, AZ, directly across I-40 from a campground. The campground is nothing fancy, but it is inexpensive. I spent the night there a few years ago and full hookups cost me $20. Then I popped across the Interstate and spent a couple hours prowling the huge selection of blades. Wound up buying a nice folding ceramic-blade that is my daily-carry.