*Mobile gaming companies with pay to play / pay to win model. They can acquire some game as it's starting to become popular on and "monetize" it through selling custom skins for players, upgrades. Endless amounts of passive income to be earned from selling pixels and all they need to do is keep a couple of servers running.
*The sunglasses industry - sell cheap bits of plastic for 100s of euro and get away with it. The pieces of plastic only last a few years so plenty of return customers
*Car insurance - the vast majority of customers just shovel 100s a year into them and all they want in return is a piece of paper with a date and a green strip printed on it
*Banks - Pull 300,000 euro from a magic bankers hat and watch some eejit paying interest on it for the next 30 years. Once you are able to set yourself up as a bank there really isn't any fear of you seeing another poor day once you don't do anything ridiculously drastically stupid.
*Paid car parks - Nobody ever complains to say the boiler in their parking space is broken, no problem evicting users, pay some fella to have a look at the ticket machine once a week or two and if your car park is in a popular spot you can throw your two legs up on a sun lounger in Barbados for the rest of your days
any more to add?