Ask HN: Do you guys know any awesome tech companies in Berlin?

After high school I want to make an internship at some awesome tech company in Berlin, as I'm going to study there.

The two well-known Berlin startups are SoundCloud and 6Wunderkinder, but what other tech companies are located in Berlin?

Readmill and Gidsy are also Berlin based. I know of txtr too, but only because they share an office with SoundCloud :-)