I’m reminded of the katana in E.Y.E. Divine Cybermancy. Quite literally it used energy to generate a bullet shield, that ran out, and it could still be used like a melee weapon, including to parry. We already have A. UPS, B. Bionics, C. Bionically powered internal bullet shields, so option D. internally/externally powered bullet shield item seems a logical continuation.
To the fullest extent, it would allow melee characters to maybe have an annoying, but at least bullet-withstanding (if only enough for one or two enemies) defense. To a lesser extent, it could be used to run by turrets and things without turning into swiss cheese.
Or just some other similar but more restricted idea, EM scrambler (only works on bots), invisibility thing (smells/sound still get through so things would come looking for you). A fun graphical effect would be making the @ not render, cause, you know, invisible.
To balance it out a little, if it could hinder projectiles coming OUT of the shield, it would be hilarious and perfectly reasonable.
If it was a dropped and applied item, maybe it could be used as a temporary means of making impassable barriers, to either block an enemy following you, or to walk by a dangerous spot without your innards becoming your outtards.