The perpetual search for the perfect mechanical pencil

[Orson]

The PENTEL P205 (0.5mm) or P207 (0.7mm) is the best mechanical pencil I've ever used. It has lasted me nearly 3 years and still works fine. If you want to keep it in your pocket, I suggest you put a pen cap on it to prevent stabbing yourself.

You can pick it up at Officeworks for around $13 or eBay, with prices from $6.

It is a no nonsense mechanical pencil that is used by professionals.

[vobinhood]

I also use a mechanical pencil by Pentel, the "Twist-Erase Automatic Pencil" (0.5mm lead). I bought it from Officeworks for just over $9. A little pricey but worth the investment
It's the best one I've ever used. It also has a twistable eraser that you were looking for.
A link for future reference: http://www.pentel.com.au/shop/step1.php?number=944

[sabxiao]

http://www.jetpens.com/Uni-ball-Kuru-Toga-Mechanical-Pencil-Starter-Set-0.7-mm/pd/10372
The uni-ball kuru togas have some crazy auto-lead-rotating technology to them, which prevents lead breakage and has a uniform line all over. This starter set comes with some of the stuff you were describing.
If you're looking for a metal body, you'll have to look in the 0.5mm unfortunately (http://www.jetpens.com/Uni-Kuru-Toga-Roulette-Model-Auto-Lead-Rotation-Mechanical-Pencil-0.5-mm-Gun-Metallic-Body/pd/6547.
But aside from that, the Kuru-togas have rave reviews everywhere they go. If these aren't to your liking, have a look on Jetpens which has the best assortment of quality stationery from around the world!

[chelonianlover]

Off topic but there is a special place in hell for people who call mechanical pencils.....PACERS!

Curiousity, what's wrong with calling mechanical pencils pacers?