Backstory:
Spoiler
I'm going to be leaving my current place of work at the end of next week (or sooner, if they realize how hard I've already checked out...)

I've been with the company for just over 4 years, in which time I've been assigned a couple of laptop computers, as well as a desktop. I'm quite well versed in Windows data handling, and I've already gone through all of my Windows machines to remove any of my "personal" data, and destroy anything else that I wouldn't want IT scoffing at

My major weakness, however, is these fucking accursed Apple devices! I generally avoid them like the plague (as the resident prime geek in the majority of my family and social circles, I find myself often providing free tech support for a multitude of issues, however, my default response for anything Apple related is "take it to the store, and get the geniuses *cough*DERP*cough* to fix it...")

I would like to know the best method to fully wipe my company-assigned iPhone 4, and restore the device to the original factory settings. I am aware that IT wizards, through their mystical wizardry, are capable of recovering surprising amounts of information from devices which have been purely "factory reset" with the built-in functionality (like the "recovery" partition on a bloatware-laden laptop, or the iTunes "factory reset" button for iPhones.)


TL;DR
What is the best and most effective method for fully and completely wiping everything from an iPhone 4, and restoring it to essentially new-in-box factory settings, without bricking the device.