Microsoft EYU00049 Surface Pen - Ice Blue - New in the Box. I pulled it out of the box for the listing picture. One of the pictures shows the original packaging on the pen.
Currently selling for $75 online.
From the Microsoft Product Page:
Create without limits

Surface Pen is better and faster than ever, with tilt for shading, [1] greater sensitivity, and virtually no lag to help you capture your thoughts and get more done.

Create uninterruptedWrite and draw with precision ink on one end and a rubber eraser on the other. Tilt your Surface Pen to shade your sketches just like you would a graphite pencil.
Write and draw naturally

Precisely sketch and shade with 4,096 pressure points that respond to the lightest touch. Ink flows from the tip of Surface Pen to your screen with virtually no lag, and the eraser rubs away mistakes.

Bring your vision to life

Compose a song, make an animated short, take notes, and draw 3D CAD designs. Use Surface Pen with apps like OneNote, Microsoft Office, Adobe Suite, Bluebeam Revu, Drawboard, CorelDRAW, and Staffpad.*

Express yourself with Surface Pen

Choose the color that best expresses your style. Surface Pen comes in four colors—Platinum and Black, plus new Ice Blue and Poppy Red—that coordinate with Surface accessories.