I haven't seen all of them (which I wanted to see) yet, I had a lot of fun with various talks. Thus far, my favourite one was hands down [1], and I can explain why. I am not at all good with hardware, nor hardware designing i.e. I'm not the target audience for this talk.

However, the talk was beautiful. It went quick, was informative, good slides, very respectful Q&A (comms and quality-wise), and it had a message of DIY _and_ inspiring hope. It is easy to criticize X or say we need to do better with Y. These guys are doing it, and their journey and findings is completely open source (even though there was substantial financial risk involved). The hacker spirit 101.

[1] https://media.ccc.de/v/39c3-in-house-electronics-manufacturi...