The King of Bokeh
I just got myself the Nikon 135mm/f2 DC. DC is for "Defocus Control", which is Nikon's patented system for controlling the background or foreground blur.
Some say this is one of the best portrait lenses in the world, so the expectations are high!
I've only been able to try it out a bit, but the technique is that the "Defocus Image Control" ring correlates to the aperture you're using. Se it to 0 and it's a normal lens, but if you use it, you set it to 2 to the "R" (rear) side if you're shooting at f2, which enhances the background blur.
Here are some test images:
