If you're trying to make a name for yourself in the incredibly crowded portable storage space, you can innovate and create something totally awesome, or you can do this. The mDock from mLogic is an external hard drive, port extender and port blocker all rolled into one pricey coffin-like chamber of fail. $219 will net you an eternal resting place for 500 gigs of data, while $299 ups the ante to an entire terabyte. Plus, with a pair of front-facing USB ports, you can add a third-party portable storage yokel for the less-than-princely sum of 50 bucks. If you haven't already gathered, the mDock is designed for mMacbook Pros, but there's also the iMac-mountable mBack (curiously not the iBack), designed with Apple's familiar desktop flavor in mind. That variant is slightly more affordable, with pricing ranging from $169 for 1TB to $349 for 3TB, but you'll forgo the dock-like USB hub and headphone jack. There's no word on when to expect these life-changing devices in stores, but it's never too early to dust off the mChair iChair and park yourself on 5th Ave.
Update: As pointed out by many in the comments most ports that are blocked by the mDock are replicated on the silver brick, including the Magsafe. The only restriction appears to be a lack of pass-through for Thunderbolt, but you do get a mini DisplayPort for hooking up external monitors. We've added one more pic after the break.
AppleiMac 27-inch with Retina 5K display (late 2014)