I just did a break, so I thought I could write a couple of little ideas that I felt that would help me with modeling and certainly would help others too -if they were implemented:
1. Continuous loop-animated lights during modeling OR animated environment map with some light pattern.
Purpose: To see clearly the bumps and valleys of your model while you work through the continuously slow-moving shiny reflections, without having to rotate each and every time the view, then return to what you were doing, change something and so on.
That would be useful in many cases, including in a two-window setup with front and side views, on top of the corresponding reference images in the background. It would be possible to do 10 times more work with no interruption. I bet it would help sculpting too.
(Just thought of another one for the same purpose although I bet this one has already been proposed):
2. Support for 3D monitor.
Nowadays you can have a 3D monitor for less than 200 euros with passive polarized glasses, easy on the eyes and the brain, albeit with half the horizontal resolution, or a bit more expensive full res 3D monitor with active shutter glasses if you prefer. So what would be more beneficial for a serious modeler than creating AND watching his/her 3D creation …in 3D?
3. Directional proportional edit with edge propagation capability.
Purpose: To do in just a few moves, what would take a lot of pulling and pushing of neighbor vertices and smoothing cycles, in many cases.
Example: You have a curved large edge and you set proportional edit to propagate along the edge with eg Smooth falloff at strength 0.7, while you set it to propagate to all other directions at strength 0.2 and Sphere falloff.
Now with the combination of shortcut keys and/or the mouse wheel you could change that setting while you hover the mouse above the edges (until you press enter).
Also, it would be very useful to use a desired oval shape (instead of just circular) and select the orientation of that oval shape.