If you really must have every gadget Apple has ever created, you might be interested in an iPhone 4 prototype which is currently being sold on eBay.
The device is sold “as is” without any warranty whatsoever, and it cannot be activated via iTunes. For the most part, it looks like a regular, black iPhone 4, but it’s marked “DF1692″ in the lower right corner of its front side, and it also lacks the “+” and “-” markers on the volume buttons.
As far as any new, extravagant features go, this prototype will not get you any, except for bragging rights. Judging by the current bid, which stands at $2,025, there are people out there who value those very strongly.