If you have the room for it, a shovel/digging tool can be of use. Digging can get you food (grubs and other ground dwelling insects to eat or as bait), water (subsurface), keep you dry (water redirection), provide shelter (snow cave or igloo), reduce risk of illness or unwanted wildlife (burying wastes) and even be an impromptu weapon. So you should definitely have one, right? Maybe not. Because most shovels are also big and heavy.
If you are in a vehicle, then having a really good shovel is worth considering. If snow is a likelihood, a snow shovel may also be a good thing to include. Otherwise, a trowel or folding shovel may be the best you can practically manage, and even that may be too much.
There are plastic trowels and standard garden trowels, but these tend to take up too much space. I don’t trust plastic that much any way. My preference is for the folding handle stainless steel trowel such as those by U-Dig-It. They have a standard weight, which would probably be more durable, but I go with the light weight version which is, not surprisingly, lighter. And costs less. I have this in my “shoulder bag” kit, and nothing in smaller kits because it either won’t fit, or would take space away from more important things.
A trowel is not a fabulous digging implement, but it is better than your bare hands, or many of the things you might hope to find in the environment.
In my backpack kit, I go with a “real” shovel. Folding, of course. I found a screaming deal on the SOG folding shovel (Entrenching Tool, they call it), and I have found their knives to be good quality, so thought I’d give it a try. It is based on the modern military folding shovel, although smaller I think. Open, the entire length is 18″ and the head is 4.5″ by 6″. Kind of toy-like, but not bad for the space it takes. Like the military version, it also has a pick built in. One edge of the head has a saw like teeth, which is too dull for serious saw usage. Probably good for cutting through grass and the like. SOG has a higher end version, but at a much higher price. One of these days I’ll find a good value in a military surplus version to try out to see if it is enough better to be worth the extra size and weight.
Note that one often suggested use for a shovel is to dig a “solar still”. Yes, such a construct will allow you to extract moisture from the ground, plant matter, and even purify some sources of water. Usually it will cost you more water (sweat) than you will get from it.