For me, it’s Gintama. It’s iconic, easily identifiable, and makes sense on a musical level. On the last point, I’m not knowledgeable on the theory, but the Gintama soundtrack, in general, is enjoyable to listen too. If I have to pick one favorite song there, it’s Katsura’s theme.
Ghost in the Shell: Stand Alone Complex and SAG 2nd Gig which is…ok Yoko Kanno at this point this is cheating.
So instead I’ll say Mobile Suit Gundam: Thunderbolt. That thing made Jazz terrifying.