We get a lot of questions about the "best pencil" to use for marking the quilt. I wish I had a definitive answer. The reality is that what works for one does not necessarily work for another.
Having said this. Here are my suggestions:
Whichever pencil/pen you use, test, test, test first to make sure it will do what you want it to.
If you are going to wash your quilt then there are some additional options.
Any chalk pencil has a tendency to break when sharpened. I use a battery powered sharpener and as it sharpens will twist the pencil. I believe this will give a more even cut. I also will mark a few inches - about 12" and then tip off the lead in the sharpener. This requires less sharpening when needed.
I also use the black graphite - also made by General Pencil Co. Since its original introduction into the art community, the company has hardened the lead a bit so it will sharpen better. I have marked on off-white cotton sateen and when finished machine quilting, the marks were almost gone and could be erased or washed.
Most that indicate for fabric are ok. A-1 from General Pencil is a good one. I also use the black oval lint brush found in the pet supply section of most large stores. This brush appears to act both as a brush and eraser as it is made of plastic.
All the above products except the Lint Brush are described in the Stencil Company catalog on their web site. You can reach them at this link: http://quiltingstencils.com/markingtools.aspx
I want to emphasise again to test before marking your quilt. Fabrics react differently to the various types of pencils.
Two cautions from quilters...
The markers that have a rolling attachment to dispense the chalk tend to embed the chalk into the fabric making it difficult to remove.
The pen that can be removed by heat or friction has some problems. While the instructions say the marks can be removed by ironing over them, but will come back when put in the freezer have had mixed reviews. While they do indeed disappear in heat one quilter said she put the quilt in her car and drove some distance in the winter in the cold car and all the marks returned. So guess we don't have to preserve the quilt by putting it in the freezer but any cold even in a cold room might cause the lines to return. Also, it has been reported the chemical will bleach out some colors. All this is hear-say but am passing it on for your consideration,
Remember, what works for me doesn't always work for you. Be careful in marking and make sure it will perform as you wish.