A short opportunity is the HKX, the Hamburg-Köln(Cologne)-Express.

Until they get their new rolling stock, they currenty are running with Avmz and ABomz cars. Avmz are Rheingold and Rheinpfeil cars from the 1960s (see this wikipedia picture) and ABomz cars are UIC-Z-cars original from the GDR (see wikipedia link) from the 80s.
Sadly they change their cars unnoticed and spontaneously, so you might end up sitting in a very uncomfortable 460 for a couple of hours ...