What is the best mechanical pencil?

Pentel P205 been using one since the 7th grade

Zebra M-402 . I have used and loved other Zebra's but this one has a nice heft to it.

I really like my Cross 0.5 mechanical pencil that matches my Cross pen. It has a retractable metal sleeve for the lead and a very nice feed action.

Cross Pencil

For super drafting action, I like this OHTO Super Promecha thing I bought at the Japanese book store. Adjustable everything and a cross-cut metal grip.

OHTO Super Promecha

I use a Pentel Twist-Erase 0.5 (QE515)

I got this from my dad, who is an mechanical engineer, and I use it as a mechanical engineering student. It works very well for me, especially for writing on all that engineering paper. I started using this in high school and have used the same pencil for about 4 years now.

I've been using the Pentel Quicker Clicker 0.5mm since I was in college back in 1982. Several things make it great:
1. The lead advance button is on the side near your fingertips. Important if you are taking a timed test and are writing as fast as you can.
2. Big eraser on top! Don't forget that you'll have to occasionally erase your mistakes. Many mechanical pencils have wimpy pink rubber erasers that are hidden under the metal cap that you have to remove every time you need to erase. The Pentel comes with a big white eraser on the end that cleanly erases pencil lead. You can easily buy replacement erasers at most all office supply stores.
3. If you buy the clear body version, you can easily see how much lead you have left.
4. They're relatively cheap so that if you lose it, you won't be upset.
5. If you don't like 0.5mm, they are also available in 0.7mm and 0.9mm.

Pentel Quicker Clicker

The best thing to do is go down to a real stationary store (not Office Depot/Max) where they have an assortment of pencils and try them out. What works for one person won't work for the next. Some prefer thinner pencils while others like fat ones with a rubber grip.

If you're near a big coastal US city, check out there Japanese bookstores and stationary stores like:
Kinokuniya
http://bookweb.kinokuniya.co.jp/ohb/02/contents/storeinfo.html

Maido
http://www.maidostationery.com/

They will have a ton of pencils for you to try. Pick up something nice for your SO while you're there.

draft/matic mechanical pencils are great.

Uniball Kuru Toga

Uniball in Japan, home of mechanical pencils, sells an automatic pencil with a clutch which rotates the lead as you lift and press the tip on the paper. It keeps a chisel tip on the lead, so you don't have to turn it. Genius conversation piece meets excellent writing utensil-gadget-thing. Looks sleek, too, and not too expensive!

Product Name

Uniball Kuru Toga

Uniball in Japan, home of mechanical pencils, sells an automatic pencil with a clutch which rotates the lead as you lift and press the tip on the paper. It keeps a chisel tip on the lead, so you don't have to turn it. Genius conversation piece meets excellent writing utensil-gadget-thing. Looks sleek, too, and not too expensive!

Kuru Toga

Without a doubt, it's the Pilot Vanishing Point H1005. I've used one of these for 30 years now (I'm on my 4th one) and it's the best pencil I've ever used. It takes 0.5mm leads, so it can write fine enough that you don't look like you're using a fat crayon. The sleeve click retracts into the body, so there's no danger of you accidentally bending the business end by somehow mishandling it. They may be out of production now, but if you look around you can still find some vendors with some. Buy two.

The best pencil out there is called a ROTRING.

They are great looking and can be purchased in a retractable model as well. You can find them new on Ebay - they are shipped from Japan.

Staedtler Mars technico with soft 2B leads.
http://www.staedtler.com/Mars_technico_780_C_gb.Staedtler?ActiveID=2204 - listed as a "lead holder".
You can put down varying amounts of graphite, a lead lasts forever, and they sit nice and solid in your hand. I've filled many a notebook with these - using a standard mechanical pencil just doesn't cut it in comparison.

I use the PaperMate PhD Mechanical Pencil and the PaperMate Dr. Grip Center of Gravity Mechanical Pencil

The PhD is 0.5mm, the Center of Gravity is 0.7mm

If you like "fatter" pencils with comfortable grips, you can't go wrong with either. I've almost exclusively used PhD pencils since middle school and haven't found anything that compares.

Pilot H1005 "Vanishing Point",
http://www.biglp.com/H1005.html

I bought two Pentel Sharp Kerry pencils when I was looking for a good mechanical pencil a couple of years ago. It is all metal quality construction, has a bit of weight/heft, and feels great. It can be capped when not in use too so you don't have to worry about poking holes into your bag or pocket.

https://www.pentelstore.com/index.php?grp=690&osCsid=f0cc4988993c09db39a867e54b6ab432

Hands down, the best pencils are from Staedtler. I have used them for years on a professional level. These pencils are a perfect example of fine German engineering.

http://www.staedtler.com/cs_mechanical_pencils_gb.Staedtler

I don't use a "proper" form when writing so I have issues with most pens and comfort(caluses) with extended use.

Long ago I stumbled upon the Sensa pen. Sensa also makes mechanical pencils in the standard .5 and .7mm sizes.

It is made of aluminum, extremely well balanced and has a heat/touch reactive grip. I've tested alot of pencils/pens and this set was by far the most comfortable.

Plus it is very stylish with the simple lines and solid color scheme(s).

Prices vary at around $40-$50 per unit.

http://www.montgomerypens.com/product_detail.asp?product_id=150

I prefer the Rotring 300

http://www.google.com/search?client=safari&rls=en&q=pentel&ie=UTF-8&oe=UTF-8 for general unless your an architect, in which case it is probably a different answer.