Sharpie Permanent Marker Pro Bullet Tip, 1 – 4 mm Chrome Season and the ink is mixable:

and the ink is mixable: touching the nib of this pen briefly against another Parallel pen filled with a different ink color blends the two on contact

It comes with a removable metal clip and a refillable eraser under the top button

which means you can lay watercolor washes

Vents137 and many more

Sharpie Permanent Marker Pro Bullet Tip, 1 – 4 mm Chrome Season and the ink is mixable:Permanent marker by Sharpie. This bullet tip permanent marker can write on most surfaces including wood, metal, stone, plastic and leather. The black special ink is water and fade resistant, and contains no xylene or toluene, meaning less odour. Line width: 1 mm.