James Dunnigan describes some popular add-ons for infantry weapons, starting with the red dot sight:
This sight, similar to the point-and-shoot viewfinder found in cameras for many years, was first used by the military (U.S. Army Special Forces) in 1970, and also became popular with hunters and paint ball gun users. The red dot sight was more accurate than iron sights, could be used with both eyes open and was generally more effective at typical combat ranges (under a hundred meters). The sight was particularly effective at night, and in the 1970s, that was its big advantage.Current devices, like the U.S. Marine Corps ACOG (Advanced Combat Optical Gunsight), does not use batteries and provides a red chevron-shaped reticle and bullet drop compensator. For daytime use, a fiber optic system collects available light for brightness and controlled contrast in the scope. At night, the system relies on tritium for illumination. The 4×32 sight allows you to get first round hits at 300 meter, or longer ranges. The sight still allows for better accuracy at closer ranges, with both eyes open. The manufacturer, Trijicon, made the original sights of this type back in the 1970s. SOCOM has long used them, and many marines and soldiers have bought the civilian version of the ACOG with their own money. At a thousand bucks each, ACOG costs more than the rifle it’s mounted on, and the users consider it well worth the price.
For a while, troops were happy with a Surefire White Light 6P flashlight taped to the end of their rifle, but now they have MFALs — Multi-Functional Aiming Lights:
This looks like a small flashlight, and attaches to the rifle. But this device can put out visible, or invisible (infrared, or IR) light. When using IR, you go into a cave providing light only you can see, with your night vision equipment. If you are real quiet (or sort of quiet), you have a big advantage over the bad guys trying to hide in the dark. This rig also allows you to see any booby traps the enemy may have laid for you. MFAL also emits a laser pointer (like the older “red dot”), but one that cannot be seen by the enemy (unless they also have night vision gear, which they usually don’t.) The MFAL was developed with the help of feedback from combat troops in Iraq and Afghanistan.