What are some useful things to create with a typical 3D printer?

I generally come across specific things that prompt me to print a custom solution for my life. I wouldn't be surprised if there literally isn't any truly useful better-3d-printed-than-purchased thing that someone can recommend for you. (But maybe I'm just not imaginative enough :))

Maybe the biggest category of things is replacement parts for stuff around your house. The $7 doohickey might cost you $1+time to print instead.

That said, here are some things I've printed for use around my house, which might give you some ideas for your own life:

• drain spouts with hose connection to route water from my gazebos "gutters" to the ground instead of just splashing down out of a hole
• a cover for the switch on my floor lamp so the light can only be toggled with the wall switch instead of in 2 places
• wall mount for my cable modem/router
• temporary oil cap replacement for my car when I accidentally lost it after changing the oil
• custom tool holders to 5-S my workspace
• large v block clamps for my drill press
• riser for my bench top power supply, to tilt it at a better angle for viewing
• infinite toys for my kids
• replacement part for a model kit that my kid accidentally broke
• handlebar basket custom sized for my kids bike
• replacement latch clip for my car's fuse cover

Just some examples of things I've printed or plan to. Ones marked with an asterisk (*) at the end are ones I largely or entirely designed myself or plan to largely or entirely design myself. Ones marked with a plus (+) are ones that are half completed. Minuses (-) are ones I haven't started yet but intend to.

• Wall mounts for Nintendo Switch components (dock, controllers, Joycon charger, etc.) Definite space saver. *
• Wall mount for a Raspberry-Pi-based NAS solution. *
• Parts to augment a computer chassis wall mount for my ridiculously-large chassis. (Yes, there's a bit of a pattern there.) *
• A custom Raspberry Pi case that mounts nicely and nondestructively to my desk.
• A custom adapter for my drill that let me run the drain in my washing machine when the motor was broken. *
• A custom plate to cover my nightstand clock face so it doesn't shine in my eyes all night. *
• A custom die for a Sizzix Die Cutting Machine for quilting use. (That one took a lot of work.) *
• A custom tool for precisely bending 16mm steel strapping (which I'd sharpened into a blade) in service to the custom die just above. *
• Custom yarn bowls for my crafty mother. *
• Custom stitch markers for my crafty mother. *
• Custom barrel buttons for my crafty mother. *
• A couple of custom mounts for SAD lamps. *
• Custom shelving for a bathroom. *
• Custom mods for some wire shelving in the same bathroom. *
• Custom mount for a reflector mirror to let me see more with the security camera on my front porch. *
• A tool for straightening 3D-printing filament. *
• Spacers for mounting a peg board on the wall.
• I also had a folding door that broke and got kinda janky. I had a few extra of those peg board spacers, and they turned out coincidentally to be exactly the right size to properly shore up that door.
• Custom shelving for DVDs/Blurays and video games. *+
• A custom shelf-drawer for my mousepad. *-
• A custom 3D printed mechanical keyboard... once I'm done writing the program for rapidly prototyping 3D-printed keyboards. *+

I'm sure I'm forgetting a bunch. And the above is only the useful things and excluding the mostly art/fun items.

I have in mind to do more 3D-printing of tools. I don't have much specifically in mind. But that custom steel strapping bender is pretty cool. Also, some of what I mentioned above is available on my Thingiverse.

Gridfinity

Just buy a 3d printer and you will find that there are a bajillion doohickeys and whatsits that you never knew you needed. Half of my house is now 3d printed.

I threw a bunch of broken glass, cold, heavy cream and sugar into the printer and I confidently said "Computer! One milkshake please!" with great gusto. I broke my printer. Thanks Jean-Luc!

Thingiverse is great, but the real benefit of a 3d printer for me is the super-custom stuff. The gap between my kitchen sink and wall is pretty small, so I designed and printed a sponge caddy that sits in there perfectly, and drains into the sink. My sunnies didn't fit into the holder in my car, so I designed and printed a little clip with a holder on it that fits in really nicely.

print another 3d printer 

Anything that custom-fits something. I do a bunch of functional prints, mostly things that are specific to something I own. I printed my wife a phone holder sized to fit her phone and case, I printed wall mounted holders for my remote and keyboard for my HTPC, and I recently upgraded to a larger printer that I used to create custom drawer organizers that fit exactly the things I need. I've also used it to print replacement parts for things, replacements for missing pieces, etc.

The most esoteric item I've printed is a tiny clip that holds the fill tube in place, in my toilet. And I didn't have to design it myself, someone else had the same problem with the same toilet and posted their solution.

I’ve printed lots of functional stuff. Custom BedJet fan routing, angled connectors for deck rails, a wall mount to hold my EV plug, etc.

Most recent functional print, I printed some of these sheet stays for my bed.

Filament printer? I'd print a couple of microSD card holders, USB stick holders, those thingamabobs that help you organize your million loose USB cables, organizing cases for card games or specific boardgames, some hexagonal organizing shelves because they look neat

That's sort of a perennial question but you can look on thingiverse for lots of designs, some of which might interest you.

Me, I need a replacement front cover for my ancient vacuum cleaner, for which original parts are no longer available. It's 3d printable but would need a fairly large printer. I might try carving from wood instead. A Shapeoko would be great for that, but since I don't mind it looking like crap, I might just try with hand tools.

• replacement parts for appliances (dishwasher wheels, feet, brackets...) • upgrades for your 3d printer (a camera holder is a classic) • if you are a thinkerer (I'm assuming you are) custom boxes for small projects (electronics and so on)

Another 3D printer

Ant nests and water dispensers.

Parts for many things that may break and are too old to find replacement or too expensive, like oven controls.

Supports for things in aquariums, like tubes or plants.

Supports for hanging keys, controllers, etc.

A bucket.

The thing is many times is cheaper to print and the things you print are specific to your needs.

• Cases for dev board and other electronics projects.
• Various spacers hard to find just right from the shops.
• Exotic lamp shades
• Cool front grille for your car.

I am not knowledgeable about how to design anything :(

But I have printed a rig for kite photography and a saxophone mouthpiece, and a headphone stand bc someone already designed them.

I recently joined the ranks of 3d printer owners. The first thing I printed where a pair of risers for mounting some hall effect sensors on my garage door mechanism. Very simple shapes but super handy.

If there's something you can buy, it's both less hassle and higher quality to just buy it rather than to try to print it yourself. A 3d printer really shines when there's something that you want that you can't buy. Custom parts, repaor parts, things of that nature. Unfortunately, that also means that the things that you print aren't likely to be something that you can plan for ahead of time

There are a lot of minor things, that are much faster to print than to get delivered. (If you can find them at a sensible price).

I printed some folding phone stands for my family to give as gifts and they've been smash hits

https://youtu.be/Gb1dH9LUMeY

Interior parts for 80s cars

Shells for atari 7800s. They are insanely brittle.

Are there any other cases you can think of where a custom-printed item is better than the myriad of mass-produced plastic items?

None at all. 3D prints are almost always worse than injection moulded plastic. Only if you need a very specific custom thing. Or it’s just convenient/fun to make your own.