I heard they are great for killing billionaires in experimental deep sea rigs

Operating parts of multi million dollar navy ships, according to articles. Not joking

They use it to control a submarine

The Steam Deck and Steam controller have touchpads which make them totally usable as a mouse for normal PC usage like web browsing

Disneyland uses Steam Decks to remote control droids in Star Wars land.

They can be quite useful in hobbyist robotics

They are the OG electric vibrators for people who can't buy vibrators.

In college I was on the robotics team. We used several different controllers to drive various robots. I made a little tank steering robot that was remote controlled from a PC with an Xbox 360 controller. I later rebuilt it to use a Raspberry Pi and added a pan/tilt mount for the camera controlled from the controller's D-pad. We also used a Wiimote to control our competition robot, using the accelerometer for steering which was pretty cool. This was in like 2010 when motion controls were still a relatively new and cool thing.

Several modular synth modules use joysticks for control over parameters, but one of the coolest I’ve seen is one from Delptronics that uses a wii nunchuck controller to send out control voltage. Hagiwo I believe also has a similar DIY design.

I do recall a gaming controller being used to pilot the titan submersible that is now on the ocean floor. May their souls rest in peace.

Some guys I used to know used them to make music, as some sort of midi controller.

We had a subcontractor drive a wired camera mounted drone through the sewers with it. Some use LIDAR or SONAR instead of just cameras. Game controllers are pretty common for these.

In Ghostbusters 2 they rigged up a Nintendo joystick to drive the statue of liberty through the streets of NYC. Does that count?

I am working on getting my XBox controller to work with a Raspberry Pi/Astroberry setup to control my telescope.

Hacksmith on youtube uses playstation controllers for remote operation of their giant mechs.

I have one of mine configured as media controls when I'm wandering around the house (8bitdo controllers ftw)

All a controller is is just some buttons on a wire in a portable form factor.

If you want to use it for Excel, you can.

I used one on a Raspberry Pi to drive a self build remote car wirelessly.

playstation and Xbox controllers make good Kodi/XBMC remotes for a laptop connected to a TV.

I used to use a mini game controller for artwork. Like up on the dpad would zoom in the canvas. I had buttons for undo, redo, switch to eraser, rotate the canvas, flip it, etc.

I think it was med students who use controllers to control flash card decks for studying.

Also as PowerPoint remotes.

I've seen some people on YouTube use them to control their CNC.

For FRC robotics competitions, we use Xbox controllers to control the robot

I don't know if me talking about my Steam controller counts...

Some digital artists use Switch JoyCons for shortcuts in Clip Studio and other painting programs.

Gave a presentation last year, using a joy con as a remote for switching slides.

Nice thing is you can have mouse with the joystick as well

On a very old computer of mine, the "y" key was completely missing and I couldn't replace it because the contacts were broken so I just use JoytoKey and a USB SNES controller.

I've also used a similar setup for navigating some image boorus but, for obvious reasons, I wont specify anything further.

I would also add VR controllers to the list and I had used them for painting.

We used a ps4 controller as a mouse on our tv/media center. Its wired/Bluetooth and comes in as a mouse on our Linux box. No setup, just connect and it works.

Scrolling around LibreELEC to get to my gaming folder

I use my flight sim gear as a fidget toy, hope that counts.

Haven't actually done it yet but I'm going to buy myself a Teensy for my birthday next month, set up headless M8 on it and control it through my Steamdeck.

Iirc (on the phone now,) cameractrls allows panning and zooming with a gamepad.

Maybe 10 years ago, I set up a controller with my laptop to use as a mouse. Don't remember if it could do keyboard too. It's pretty nice ergonomically if you're just browing and not doing serious work.

Typing with Donkey Kong Bongos