I often discuss Jane Street as a great model of employee branding. They do well placed adverts/sponsorships (e.g. Standup Maths[0]), they produce a quite decent quality podcast (Signals and Threads [1]), and they have consistent monthly puzzles [2]. That level of investment in branding only makes sense, I think, at a large size. I'm kind of surprised they only have ~2500 people.
[0] https://www.youtube.com/user/standupmaths [1] https://signalsandthreads.com/ [2] https://www.janestreet.com/puzzles/current-puzzle/