Lightroom's Radial Filter Tool is one of the most useful local adjustment features in the program, allowing you to easily mask in a wide range of changes. While most of us are aware of its utility, this great video provides a few tips and subtler features you might not be aware of.
I personally love the Radial Filter tool. I use it to draw attention to the subject in environmental portraits or event and wedding shots, the feathering making it easy to subtly mask in a light vignette that doesn't look corny. It turns out that the Radial Filter tool is far more useful and versatile than just adding exposure-based vignettes. In addition to using it to mask in white balance adjustments, clarity, saturation, sharpness, and more, you can create any elliptical shape, extend beyond the boundaries of the canvas, create a full-size vignette with one click, and even use it in tandem with the Brush Tool to erase away areas of undesired adjustment. I'll frequently use this trick with musician portraits by using a small radial filter to draw attention to their face and instrument, then erasing away the borders of their instrument to keep it nice and bright.
[via Shutter Bug]