If you plan to wash it, I love the Crayola Ultra Clean markers or crayons. Just to be completely safe, I'd test whatever color you plan to use on a scrap to make sure it comes out okay. Sometimes people report issues with the Yellow marker not coming out. I usually pick green, blue or purple on white & they come out no problem even with white on white fabrics. The crayon usually comes out partly just during the quilting process, and the rest by brushing it off with my hand. If there is any remaining, I can usually get it out with a damp rag.
But really whatever you like is a good choice. I have seen quilts where the #2 pencil didn't come entirely out but it's usually only noticeable when looking for it since you stitch right on top of the drawn line. I've heard that either the white or kneaded erasers get out stray marks better than the pink erasers. I know that's the case with stray marks on clothing.