I was looking around Ebay for some electronic components and I stumbled upon this:

0.2mm Nozzle Extruder Print Head for 3D Printer Makerbot Mendel RepRap NTC 100K


I think it's a brilliant design, the hotend heatsink is combined with the extruder body and that makes it amazingly compact, I haven't seen anything like it before.
It would seem to have many advantages compared with a J-head or E3D hotend, of course it is much shorter which increases the maximum print height, also it should be more rigid and reduce "ringing" when printing at high speeds. Also the short filament tube should reduce friction when extruding and the heatsink can also cool down the stepper motor. Me likey!
The only issues I see with it is that it doesn't seem to have mounting holes and it may be difficult to access the extruder to clean it.

It got me thinking that it could be easy to build something like this from scratch, a L section piece of aluminium extrussion to mount the motor and a threaded hole at the base to screw in a shortened hotend barrel... or maybe I'll just order one to try it...