A laser tag gun consist of the following parts

The laser

The laser is the most important part of the gun because without you can fire at someone. First of there is no laser in a laser tag gun but a led with a lens. The most important reason for that is that the focus point of the laser is far to small. The laser is not using visible light but IR to make it harder to spot people in the dark.

The receiver

Able to fire at someone is nice but able to know when get they get hit is almost as important. To know when and where someone hits you, you some kind of sensor that can detect the light form someone’s gun. The sensor need to be placed all over the gun and even some on your body to cover all corners.

Controller

The controller is the hart and brains of the gun. The controller need to run the software that connects everything together. The controller needs to have some IO to connect to all the different components it doesn’t need a lot of cpu power. So the best option is a

Screen

The screen is to see you lives/health/kills/ammo/stats/more. RGB is not needed 1 color is enough. The simplest options is a common 16x2 character LCD screen, the more premium option is a oled screen it gives a lot more option.

Power

You don’t want to have to recharge or swap battery mid game. Normal AA battery’s are a option but a rechargeable battery’s is the best option. There are two common types of rechargeable battery’s Lipo and Lithium.

Communication

Communication between guns and maybe even with a base station. There are several ways to communicate (WIFI/Bluetooth/433mhz/Lora/) they all have several pros and cons. Which way you want to use really depends where and how you want to use the guns.