Great list so far!!

Here's mine::

-Transform object to follow along a curve.
-2d Flattening of a 3d object.
-Variable width fillet.
-Improved Blend.
-That-Astounding-tool-that-only-the-author-of-this-software-can-imagine.

I would like Instances but only if it's relatively easy to implement as I rather see improvement in modeling.

Marc