Watercolour usually means either pans of paint, or pencils. But Faber-Castell's Albrecht Durer brings artist-grade watercolour to marker pens. These wonderfully versatile markers have two tips, so each marker is both a standard 'bullet' tip marker and a brush pen for more expressive strokes. They're pigmented so the results are highly lightfast, but they also blend easily with water.
Along with a choice of sets, individual pens are available, so you can replace pens as they're used, making them more economical to use.