Really depends on the urgency of the task I'm working on.

Crunch time: hardstyle/hardcore for the mindnumbing tasks (early 2000s compilations), folk (like Heilung - to get in figh-or-flight mode), or percussion (Slagerij van Kampen is awesome!)

Chill dev-days: Piano guys, jazzy/country/classical playlists, trippy stuff like Shpongle or dead can dance