This gun when charged up can actually shoot through walls, as well, as demonstrated by the Barney
just before you get it. You hear him talking about the gun, the scientist telling him to be careful, a zap and a bunch of boxes outside the room explodes. Apparently he overcharged it and it zotted him and the scientist both.
Very useful for popping the snipers that hide in camoflagued holes in walls later in the game from around a corner. It's kind of hard to aim, though, as you have no way of actually seeing through the walls to aim well.