Ask HN: Which recruitment agencies should I avoid? (Europe/World)

I am a software developer and started freelancing a while back (2-3 years). For the first time though, I got a project through a recruitment agency/company. I had a mixed experience, had to go to a lawyer to clear things up. This showed my how difficult it can get to get your money etc.

So I want to use the combined knowledge and experience of HackerNews to create a list of agencies with good and bad reputation.

(Maybe this can turn into a website).

So, please share your experiences with certain companies so other people can avoid those.