I don't know for iPods but for iBook cases a smooth guitar pick is the best to unclip the case. It would probably do a great job for opening iPods if your sharpen a bit the pick edges. With this easy to find and cheap tool you'll never damage a case. When working inside a machine the spudger tool is what you need to avoid damaging the internal components and to easily disconnect the small connectors from their socket. I also use magnetised screwdrivers. I have a bowl with a magnet inside and that's where i keep my screwdrivers.