Is there a "perfect" (temporary) marking tool?
 

From what I have read:

The "perfect" (temporary) marking tool will

- leave marks that stay long enough so that one can quilt the item (or place the applique pieces) however long after it was marked
- will be completely removable
- will never show up after one thinks they have been removed
- do not damage the fabric in any way
- will not turn the fabric a funky color years later

So far, from what I have read - the Crayola ultra-clean washable markers and marking with soap slivers seem to come closest to fitting the above criteria.

Crayola gets my vote.. I love them things. I have never tried soap.. interesting

The white ceramic pencils get my vote.

(Of course, this is only good for fabrics with contrast.)

The grey ceramics are good for lighter fabrics.
However, I find they show more-so after the fact,
causing "work" to remove them after the fact.
While I use them, I wouldn't call them the "perfect" option!

i love the soap slivers... have purchased the washable markers but haven't used them yet

White chalk and blue water soluble markers. I took classes from Jamie Wallen and he said that there was no reason for anyone to invent anything else.

I tried Crayola--but the green didn't wash out.
I love the soap slivers because they are free and easy to wash out--if I'm washing the quilt. Not good for gifts.
I really love the air erasable pink Trace'n Mark by Nancy Zieman. Humidity level determines how long the marks remain.
And in most situations I like Frixion pens, but I found out the hard way I need to test the fabric as sometimes a white line remains after ironing. Great for white fabrics.
My favorite quilt marker is Dritz Tailor's chalk in the green and white pen. Very thin line of chalk that will erase but stay while I quilt. However, I can't mark the whole quilt as it does rub off.
I'm not sure there is a really perfect marker, but there is the perfect marker for every situation.

Sewline pencil or plain ordinary school chalk

These are the two options I use too :-) LOVE the blue water soluble marker.

I've been working with Golden Threads paper. You mark the paper, pin it on and quilt over your lines. Then rip off the paper when done. Even the little pieces come off easy.