I like using mechanical pencils but their big shortcoming is a tendency for the narrow tip to bend, which makes the lead break prematurely. This is especially a problem if you carry the pencil around; they tend to last much longer if they stay on your desk. Pilot has a mechanical pencil which neatly solves this problem. The tip is retractable, so it is protected when it's in your pocket or your briefcase. It also, as a side benefit, means that it's less likely to poke holes in your clothes. Plus, it's a good looking piece of writing equipment and has a nice heft to it. I've stockpiled spares in case Pilot stops making them, but maybe wider familiarity via Cool Tools will keep them in production. For me, it's essential equipment.