I'm with Ckcowl - I use a regular pencil - #2 soft lead. I do use a mechanical pencil though so I don't have to sharpen it all the time. When I have very dark fabric I will use the white mechanical pencil by Bohin (sp). I, also, have never had an issue removing the lead pencil lines from any fabric be they LQS quality or lesser quality fabrics.
I can't tell you how many other marking pencils/tools I have stashed in various places and never use. I could probably open up my own marking tool store!