Cabinet Hardware Jig
Some people consider 3D printers a novelty item, but they have many practical uses as well. For example, the typical cabinet pull template found at the big box home improvement stores can be very limiting. Get your pull right where you want it with this jig that can be generated on the fly with the dimensions that you specify. No modeling required! Common pull placement guidelines can be found here.
Wall Plate Cover
If you like keystone-style wall plate covers, you'll love this. Use your 3D printer to create custom wall plates for outlets, switches and a wide variety of communications connectors with this slick model. Simply select the size of the junction box (up to 4-gang) and pick all the ports you want to have and your model file will be generated instantly. The most common type of household 3D printer uses FDM (Fused Deposition Modeling) technology to create small plastic objects by melting successive layers atop one another.
Roof Vent Cap
One of the most common filament materials, ABS plastic, is inexpensive and most of the items in this series can be printed for less than $2 in material. For example, if rodents have chewed up the lead vent caps on your roof, you can avoid costly anti-squirrel vent jacks by simply replacing them on the cheap with replacement caps that have been 3D printed in ABS plastic. For whatever reason, the critters don't seem to chew up the ABS caps! You can find these caps freely available for download here.
Don't be intimidated if you can't do 3D modeling; websites such as thingiverse.com allow the collaboration and sharing of hundreds of thousands of object models that can be sent to your 3D printer, many of which are customizable where you can enter measurements and have your own custom object generated quickly. Battery adapters such as this one can allow a AA battery to be used in place of a C or D battery. The capacity of your AA will be less than a true C or D battery, but it'll still come in handy as a temporary fix to get you out of a bind.
Cyclone Dust Collector
Tile Leveling System
Some might consider this cheating, but we think it's quite clever. Print out a tile leveling system such as this one for your next tile job. The wedges reduce 'lippage' by pulling adjacent tiles onto the same plane.
Pocket Hole Jig
Arguably the most useful woodworking jig in existence, the pocket hole jig. Just another great candidate for 3D printing, as illustrated by this freely available pocket hole jig model. Go search around your favorite 3D model website and you will see that there is certainly no shortage of woodworking jigs in the world of 3D printing. Amen to that!
Adapters and Fittings
No, it's not glamorous or as ground-breaking as a 3D-printed lung, but adapters such as this one have practical uses all over the place. There are tons of fittings and adapters made available by the 3D printing community for everything from garden hoses to vacuum hoses. If you need it, chances are someone has modeled it and made it freely available.
How better to store and showcase your tool collection than to have a well-organized pegboard. This is just one set of handy pegboard hooks you can 3D print. Search around and you will find more pegboard hook models than you can shake a stick at! And one final note, if you want to get fancy, flexible materials such as TPU (ThermoPlastic Polyurethane) allow you to create things such as belts, low-temp gaskets, cell phone cases, grommets and wheels. Your imagination is the limit!