Step Up is great for your shelf. I'm a Casefiles fan, and IM Casefiles is pretty good for the shelf.
Pocket Medicine is a must have on the wards (3rd or 4th edition, there is not much difference)
I'd also recommend talking to your schools library and see if they can provide you a code to download a free app that might be of use. Some schools do this (uptodate, dynamed, etc...). It's nice to have useful apps on your phone you can quickly pull out and look something up with.