For dark fabrics my favorite is the Bohin chalk pencil. It's white and pink and if you Google it you will find places to buy. For anything else I just use a black ink pen. I've tried some fabric marking pens, but they get on my acrylic ruler if I'm drawing a straight edge, and in general I don't see an advantage (others may now chime in with the advantages!) and they're just more expensive. Regular ink generally comes out with hairspray and then a wash, even if it's already set in the dryer (YMMV).