I'm surprised it hasn't be mentioned yet.... use the new Kodak Portra 400, you can push/pull that film at least two stops in either direction without needing a push/pull in development with some very pleasing results. Especally the 120 size. I've shot up to 1600 in 120 and 800 in 35mm. The colours become punchy and you get a great contrast.

Shot on a Rolleiflex 2.8F, Kodak Portra 400, exposed at ISO-1600, no push in development.