Deep dive coding: psytrance and goa, some electronic and industrial works too but mostly trance. Repetitive bleepy stuff with high BPM, as little lyrical content as possible, ideally really long playlists/mixes. I have a few psytrance lists saved on Spotify :)
General coding: almost anything, although a lot of industrial, electronic, rock and metal. If I'm struggling with focus I might go with triphop, dub or generally downbeat stuff.
Bugfixing or "I have a really tight deadline to deal with" coding: metal or something angry. Really stubborn bugs get the White Zombie treatment, I don't know why that works but it does.
More often than I'd like to admit: absolutely nothing, I just forgot to take off my headphones when the music stopped and it's quiet in here and please go away I'm coding.... ;)
The anti-answer is probably worth noting too... I really REALLY struggle to work if people are playing mainstream/pop stuff on speakers - I can't tune it out and I get really tired really fast trying to do so. In fact almost anything on speakers is bad. I think there should be a 100% headphones rule in open plan offices - even if you all love the same music, it's unlikely you want to listen to exactly the same thing at the same time at the same volume.