Aluminum iPhone 4 Phillips #000 / PH000 Screwdriver
We tried half a dozen different precision Phillips #000 screwdriver tools to find the one we liked the most. The body is made from a single piece of aluminum and has nice knurled grips. The end-cap rotates so you can keep the body steady while rotating. The tip is nicely machined and is magnetic so it holds the miniscule screws in place while inserting/removing them.
These small Phillips screws are used in iPhone 4G (not 4S) and nearly every other kind of small electronic device that has tiny screws. Check the bottom of your iPhone if you're not sure whether you have Pentalobe or Phillips #000 screws.