I'll make it easier for them. Here's why I would buy each one.
Night Vision Devices--------------They would be more of a novelty to me, so I would most likely be of no use to me.
night flashlights-------------------I didn't know they made a day flashlight.

I like to see where I'm going in the dark.
gas masks-------------------------they look cool
High capacity magazines---------I don't always like to reload every few rounds during a shooting secession.
Bi-pods or tri-pods for rifles------They improve accuracy