If you've been following my website for a while you've no doubt read me yammer on again and again about 3D printers that can only use low-melting point plastics as feedstock for manufacture. Usually ABS or PLA plastic, because they're cheap and relatively easy to acquire. Joshua Pearce and his research team at Michigan Tech announced late last year that they've developed an open source metal deposition printer for fabricating tools and components for which plastic isn't appropriate. Their printer lays down thin layers of metal instead of plastic to build up much stronger objects. The total cost to construct one of their printers is approximately $1500us, which is much less than commercial metal deposition printers cost just to rent (let along purchase feedstock for, or purchase outright). It's based around a MIG welder, which is a fairly complex piece of equipment in and of itself, so it's not likely that you or I could just whip one up in our basements (well, maybe you could, I'm a software kind of lifeform). If you're curious, the bill of parts, greyprints for fabbed components, and assembly instructions can be downloaded from this Appropedia page.
In a similar vein, the company Aeromotions has created a 3D printer that doesn't use metal for feedstock but carbon fiber. Carbon fiber is very light, very strong, and somewhat difficult to work with at the best of times, so the MarkForged mk.1 was invented to simplify the process. It's capable of using carbon fiber, fibreglass, nylon, and PLA as its feedstock, which means that anything fabbed on it is potentially five times as strong as ABS plastic. The mk.1 is also desktop sized (22.6" tall x 14.2" wide x 12.7" deep) so it's ideal for microfacture of specialized components as well as prototyping in the lab. The actuators that position the print bed are also incredibly accurate; once calibrated it can be positioned with an accuracy of 10 microns, which gives an idea of how accurate this device is. On the other hand it's kind of expensive - the mk.1 costs in the neighborhood of $5kus so it's not the sort of thing you can just put on your Christmas list (and if it is, e-mail me and I'll send you a link to my Amazon wishlist :) ).
If you've ever built your own 3D printer you're aware of what a production it can be. They're complex, finicky beasts even though a considerable amount of work is going into making them simpler and more consumer friendly. Boot Industries announced recently that they'd taken a significant amount of frustration out of the process by developing a self replicating printer that only takes a half hour to construct. The BI v2.0 was designed to be as simple to assemble as they could make it while still being able to print out as many of its own components as possible. It's also entirely self contained, so you don't have to jack it into a computer, it can read gCode meshes from an SD card and run autonomously. On 22 January 2014 their Kickstarter campaign was funded to the tune of $210kus, so expect to see them hit the market sooner than expected (and with much higher quality components).