Ask HN: What would you do with arbitrary RCE on every computer in the world?

Consider it a thought experiment. If you could remotely execute arbitrary code, on any computer in the world, right now, what would you do? The question is intentionally vague, as there are many technical questions to consider (online/offline, duration of access, mobile/desktop/server/router, persistence...) that are interesting questions on their own. And plenty of enthical questions too, I expect.