Writing code and debugging code mostly. Makes you super productive if used right.

Ask it to summarize an argument or a person's intellectual stance on something. Quick summary that's better than e.g. Wikipedia or googling

I use various AIs through Kagi Assistant, often as a sparring partner to discuss ideas I have. I've used it as a legal advisor to get an overview of a field and my options, before involving an actual legal advisor that charges money. I use it as a conversational partner to practice Spanish. When someone I know was about to go through a medical procedure, I used to to learn more about how that procedure worked, how to prepare, what to expect etc.

I use it for coding as well, but very targeted, often focusing on single functions. Since I mostly work alone, I like to use it for code review, although it's frequently a bit too sycophantic.

I use it instead of a search engine.

I used it to send pictures of my broken garage door and tell me what to do

Said same thing my wife said, “RBD, we need to call a professional.”