Generally speaking, tactical flashlights will come with one of three different type of switch. Again, you need to consider the activity you will be doing to choose the switch that is most adequate for you.
The head/tail switch is very common on very small flashlights because it doesn’t take up more space in order to develop a flashlight that changes electrical contacts, which are based on how much the head or tail is screwed on. These aren’t terribly reliable as sometimes the head or tail becomes entirely screwed off and you lose it. Having said that, a flashlight with this setting is generally going to be inexpensive and suitable for leisurely use, such as a family camping trip.
The body switch is more popular because it allows you a variety of grips on the flashlight while also being able to switch it on or off. In the case of a flashlight with multiple light settings, you generally switch once for on, twice for setting one, three times for setting two, and so on. This is useful for casual use, such as rummaging through a dark shed or walking the dog in the evening. It will not dramatically enhance or hinder your use of the flashlight in self-defense.
The tail switch is the most popular and most common. With the switch at the base of the flashlight, you can alter the lighting with the “icepick” grip, allowing for better accuracy and self-defense. It is the preferred grip and switch for using a flashlight with a handheld pistol, such as when police officers use a flashlight and gun, as it allows you to aim with ease while keeping the flashlight in a position ready to strike a potential attacker.