I work for Guru Technologies writing iOS, web, and android apps.. as well as anything else our clients ask for.
After working in the field for users for a company that contracts with various businesses I've worked with so many technologies it's not worth listing and I'll probably be outdated next week. At time of writing, my favorite language for an API is Ruby (with grape, sinatra, or rails), for a frontend web I like to use angular, and for mobile I prefer flutter.
I'm excited about the coming of language interoperability, new technologies based on web assembly, increased use of AI in software, self driving car tech, and fuchsia.