For me, one the most striking and pleasant things of the CCC is that it's organized ENTIRELY by volunteers and financed by entrance/membership fees (as far as I know) so there is NOT ONE commercial sponsor to be found. I really really value this highly because today there are almost no places left that commerce/business hasn't invaded yet (most IT conferences feel like marketing events of FB/Google/Microsoft/...)
I haven't seen many (any?) conferences / congresses of this scale that are organized like this (the Burning man might be an example of a similar event, not sure how they finance it though).
And of course the people are amazing and very friendly, and it's a safe space to really be yourself. Also, they really try everything they can to make everyone feel at home, there's even an entire floor dedicated to children (with projects, games, workshops, theather, ...) and one day dedicated especially to young hackers. Where else can you find this kind of stuff?