My go-to recipes are pot roast, chicken soup, phở, and bolognese sauce. Basically, any recipe that requires boiling or simmering for a long time (and/or can be made in a slow cooker) can be made faster and (more importantly to me) tastier by the Instant Pot.
I make indian dishes mostly, Dal comes out perfect. I cook veg, like green beans - only takes 3 min (5 if you add warm-up time) which otherwise will take 20-30 min. I also cook pasta - low pressure for 6 min gives perfect la dante!
What do you cook in there that you've really enjoyed?