I have a selection of Apple products and it seem each has at least one crazy type of screw or needs some odd tool. After years fo frustration I ordered a Pro tool set. It's great but I'm still missing the screw driver for the iPhone 4s.
The first repair job was to replace an iPhone 3g front glass. The parts from iFixit were perfect and it only took 10 minutes to follow the online instruction and finish the job.
If you order the pro tech base tool kit - order the iphone 4s screwdriver because it's not included