I've tried all the suggestions made so far by other commenters, and they are solid options IMO. One of my personal requirements has been that the writing tip is either smooth/rounded, retractable, or covered in some way, because I use my pencil a lot every day, and I prefer to keep it in my hip pocket. If a fine tip is exposed, it gets caught in the fabric and/or bent.
For a long time the GraphGear 1000 was my favourite because the tip retracts and it has a sturdy metal body. But it's quite long and heavy, and I had to use the clip, which has a somewhat flimsy hinge joint. If the clip gets ripped off (happens to me) it renders the pencil useless because the clip holds the tip out for writing. I also used Orenz pencils for a while because I like the lead-protecting sleeve, but the tip doesn't seem to be designed to be repeatedly pushed back into the body, because they always start jamming on me pretty quickly.
A few months ago I discovered the Pentel Kerry and it's my new favourite. It has a removeable cap to protect the lead when closed, and to use it you remove the cap (friction/snap fit) and put it on the other end of the pencil like you would with a regular pen. The tip of the cap has a spring-loaded button which connects with the lead advance button on the main pencil body, so you can click on the rear end to advance the lead as normal. Unfortunately I don't think there's a metal body version, but the plastic feels quite sturdy to me.