Just a few notes about mechanical pencils I own.

OHTO Promecha SP-509P

Nice-looking all-aluminium construction with over-sized knurled grip. I find it good to use, but some might find it too light. It is also a bit short for large hands.
The strong chromed pocket clip is removable. The chromed metal push-button shows the lead size on the end and removes to reveal a replaceable eraser with clearing pin.