Klein Tools 56222 Penlight

It is impact resistant to 10 ft (3 m), which covers the usual drop off a step ladder or out of a shirt pocket onto a concrete slab. The body is also water resistant, so light rain or a damp crawlspace is fine. Water resistant is not submersible, so do not expect it to come back from being dropped in standing water.

The 56222 puts out 36 lumens from an LED. That is a focused pointer-level output, sized for close work: reading wire markings inside a panel, checking terminations in a junction box, or tracing a conductor in a ceiling cavity. It is not a work light meant to flood a whole room, so if you need to light an entire mechanical space, pair it with a larger area light and keep this one clipped to your shirt for detail work.

It runs on 2 x AAA batteries, and they are included in the box. Runtime is rated at 5 hours, so for crews doing full-shift service calls it is worth carrying a spare pair of AAAs in the bag rather than counting on one set through a long day.

That is what it is built around. The rubberized power button has a soft-on action for momentary pointer lighting and clicks to stay on when you need both hands, and the cushion-grip handle over the aluminum body keeps it from rolling out of your grip. A sturdy clip holds it on a pocket or shirt so it can be aimed hands-free while you work a meter or a screwdriver.

It measures 5.375 in (136.5 mm) by 0.688 in (17.5 mm) and weighs 0.10 lb (0.05 kg). That is pen-sized, so it rides in a shirt pocket or a tool pouch pen slot without weighing anything, and the clip keeps it from sliding out when you bend over a panel.