Best dungeon for me is Wanderers Palace NM (because HM just sorts of annoying lol) because I'm a scholar :3
Tam Tara HM is great as well for atmosphere
Aetherochemical Research Facility music and the coil crossover boss <3

Most others I got sick of due to regularly running them in DRs... even started to RQ if I get AGAIN Brayflox NM in DR leveling... getting it 6/7 times is so damn grrrr and even made me stop doing DR leveling at all these days :/