For the general purpose AR, a dedicated weapon-mounted light is a popular accessory, whether mounted on the rail or the vertical foregrip. If you're using a remote tape switch with your light, there are a couple of critical points to watch for. These tips are from Gun Digest author Scott Wagner, from his book Own the Night: Selection & Use of Tactical Lights & Laser Sights.
If you use a light with a remote switch, check two things. First, make sure the wires don’t touch any “hot” part of the gun, like the barrel. This may sound like a no-brainer, but sometimes one loses attention to detail.
In 1997, when I took the required training to be a certified law enforcement “Assault Weapons” instructor through the Ohio Peace Officer Training Commission, I was shooting the course of fire alongside an officer from an area police department who was equipped with an M16A1 and one of those new-fangled, yet el-cheapo, laser sight things designed to mount on a rifle. His A1 had the pressure switch for the laser taped to one of the flats on the triangular handguard and the sight was mounted on the front sight triangle. The cord to the switch, a coiled affair like an old telephone cord, at some point due to movement from the shock of recoil or improper positioning, came in contact with the barrel and in very short order burned through it. He was done with the laser.
I really didn’t get to see any of the laser sight actually being used, it was toast on the second day of class when we began live fire. I have to admit though, that I thought even then that the concept of a laser sight on a rifle was way cool. However, the Crimson Trace Laser Grip that I had mounted on my Colt 1991A1 Commander functioned perfectly. I saw then there was potential for rifle mounted lasers, just maybe not with that arrangement. I mention it now because the same thing can happen with remote switched lights.
Don’t wind cords through the openings in a quad rail, because the aforementioned will, at some time, happen.
Second, don’t tape them to the receiver either, it gets hot too. Make sure the wire is secure in addition to being out of the way of heat. Try and get a system with the shortest cord possible and tape it to the rail and/or vertical foregrip so there is nothing dangling. Don’t let the excess hang free or it will hang up.