What seasonal job do you recommend, and which one do you not recommend?

From time to time, questions appear here - probably mainly from young people - about how they can earn some extra money. The summer holidays have started too, and some young people will probably want to earn something on the side. If you have any personal experiences in this topic, please write in which directions, industries it is best to look for such temporary jobs for the holidays. Where can you earn the most, where is the work easier, and where is it harder and more stressful? Maybe there are some activities in which, apart from earning money, you can learn something valuable that could be more important for the future than just the earnings. Maybe there are some jobs that, on the other hand, you advise against? According to your experience, is it not worth getting involved in them?