To play it safe wherever you're in the world you should bring a form of identification. It might not be needed if its a small town helicopter ride.
But big city helicopter services tend to ask for forms of photo I.D. before you can fly; so play it safe and bring your passport along.
Once airborne you will absolutely need to bring your phone to take pictures, better still a digital DSLR camera will be ideal for taking professional shots.
farther to that, don't forget to bring sunglasses as the sunshine might be unavoidable, even if you don't intend to wear shades.