Clearly Tony Stark has spent some time upgrading Black Widow's outfit from slinky leather number suitable for ninja moves to tech-powered super catsuit. It would seem that she's been fitted with added pulse-weaponry that can fire from her knuckles (presumably because when fighting robots, it's better to have some sort of armoury unless you're a Norse God or a Hulk). Obviously there's nothing cynical about the fact that the power trim runs down her contours at all... The question of how her suit is powered without an arc reactor is pretty pertinent, but presumably the weaponry probably doesn't require the same power-load as Tony's higher functioning suit. And anyway, everyone should be suitably distracting by her shooting lasers out of her fists to care. Incidentally, why in the face of danger does Hawkeye look so smug?