It is not always easy to pick a good gift, but giving people tools to support their hobby is almost always a safe bet. Shooting enthusiasts are particularly easy, because they rely on a relatively small number of tools in large quantities. That means that there are a few great gifts that they will almost always appreciate.
Most shooters prefer to shoot at a club or range. Most of them have facilities that make it much more pleasant to shoot, and in many cases they are the only space that is available. That is particularly true for shotgun shooters who prefer to shoot trap, skeet, or sporting clays, since those all rely on special equipment that most people lack.
Unfortunately, those clubs tend to have expensive membership fees because they need to pay for a lot of space in spite of having a relatively small number of members. Covering the membership fee for a few months can make a great gift for a shooter, especially if they live in an area where being a member of a club is necessary.
Ammunition is the single largest expense for the vast majority of shooters. It is possible to get ammunition that costs about a quarter per shot in some calibers, but that ammunition tends not to be very good. It is much more common for quality ammunition to cost as much as a dollar per shot. That adds up fast, and many shooters hit the range less often than they would like because they have trouble affording ammo.
If you choose to purchase ammo, be very careful about the details. Performance varies dramatically across different brands and even different loads within a brand. When in doubt, find out what ammo the shooter normally uses and get a few boxes of it.
The cost of ammunition encourages many shooters to take up reloading, a process where they take individual components and use them to build their own ammunition. Many view it as a hobby in its own right, and there are plenty of shooters who would love a gift of reloading supplies. Getting them new brass is often the best bet, but other supplies can also be appropriate.
Shooters recognize that proper safety gear is vital for their hobby. Replacing a lost or broken piece of safety equipment will always be appreciated. Ear protection is usually the best gift in this category, since shooters are prone to misplacing their ear plug, and many like to have a spare set for guests at the range. Safety glasses can also be a good choice, especially for people who have a habit of misplacing them.