I know this has been talked about before, but I wanted to talk about it.
That thing to the left of the screen is called a Fulton MX991/U Flashlight, which is an angle-head flashlight you may have seen on commandos and whatnot. It's also sold to civilians, and I actually have one that is from the Army. The civilian ones are the same, and there are also ripoff versions that don't have the "FULTON" name on it.
These lights have a clip on them that you can put on a pocket, vest, strap, etc. Which you can see that's what they were going for.
These lights have different filters that you can place in a cap over the bulb. They are red, blue, and white. There's others too but these are the most common. You could also use it without a filter. The red was for night vision pretty much. It keeps your night sight (your eyes stay adjusted to the dark). The blue is for when you just needed a little light, and wanted to not be seen by enemies, and the white was for signaling and for reading maps IIRC.
I assume it worked just like the NVG only the screen was tinted red instead of green. I think they replaced it because the game is set in a near future, and these flashlights would be pretty useless when competing against aliens, and NVG headset would be more practical and believable, and wouldn't require the little icon on the side to show the flashlight, and that might've saved some space to make the game run just a little faster.