I'm a bit of a pen fanatic. I love all kinds of pens and pencils, from gel pens to fountain pens and mechanical pencils. When I went to Japan (a wonderful country for pen fanatics) a couple of years ago, I bought a Zebra brilliant multi-pen, which had black, blue, red and green ballpoints in it. I've used it a lot, so the ink has almost run out, and I couldn't find any suitable refills for it. Multi-pens are often a little more bulky than single colour ones, but I love the convenience of having multiple colours with only one pen to carry around. One thing the Japanese Zebra pen lacked, though, was a pencil.
I've just got another Zebra multipen -- the Airfit 2+S pictured above -- which has a black and red ballpoint and a mechanical pencil. It has seen heavy service recently with all the marking I've been doing. I like to write comments on the scripts in red (sometimes a lot of red), and comments on the mark sheet in black. I write the actual mark in pencil until I've had a chance to check all the scripts again and make sure that I haven't had a moment of idiocy and misjudged a paper. The Airfit is great for this, because I can just use one pen and click between the functions. It makes me feel like some kind of marking superhero, which -- half way through a stack of scripts of a certain height -- is absolutely vital to my mental health.
The pen is a bit slimmer than my old Zebra because it has 3 functions rather than 4, and you rotate the barrel to select the function, which has a nice positive feel. Both the ballpoints and the mechanical pencil are of good quality, and I know I can get refills.