After trying a dozen pedometers, I discovered the rugged, well designed Timex 5E021.
The display is large enough to read easily, and the construction is sturdy. The belt clip never slips off. It clips securely to a belt or even the elastic band of a pair of athletic shorts.
Every other pedometer I tried had serious design flaws. Battery doors fell off, belt clips broke, and buttons were positioned so it was easy to accidentally reset the units. Many of the other pedometers I tried were overly sensitive to belt position. If the pedometer was too far to the front or back of my waist, the step-count and distance would be off by as much as a third. By contrast, the Timex is easy to position (right over the hip bone) and is always accurate. The reset button is positioned so it will not reset accidentally.