About flashlights and other illumination devices.
For most of my campaign (against cultist humans) I used the Flashlight (FL) to lit large areas. My usual MO was to throw FL far away and hide in darkness taking potshots from. Electro-flares (3 wgt) were used to create an illuminated circle around my troops. The only disadvantage to this was the weight of 7 the FL as it required every participating soldier to carry one. Unused ones left on the ground (starting tile) of say, a car, chopper, land rover, etc, will illuminate the starting area, which was terrible in turn one.
Eventually the cults were defeated and aliens/hybrids were the main targets. They have better night vision, hence all of these battles are fought at day time.
Also better versions of the electro-flares (3 wgt) were discovered, such as trace-flare and the elerium flare (4 wgt). The latter can lit an area almost equal to a FL, if I remember correctly. The drawback is it needs to be thrown to activate, not just dropped as the FL. This means, I haven't sold my FLs just yet.