Nokia Lumia 710 or any decent smartphone with camera and Evernote
I use a Windows Mobile phone only because my 3,700-entry contact list keeps crashing Android phones. Why my Nokia Lumia 710 made it on this list is because of Evernote. Whenever I do a project, I snap pictures of the install (server, router, and so on) with Evernote and let it synchronize. Then when I get back to my laptop/desktop, I play cut/paste to put together notes describing the equipment. Snaps of serial numbers, insides of servers, front panels, cabling, the list goes on. Everyone wants better documentation, and Evernote makes it a whole lot easier.