I do love a highlight. A little subtle glow to the cheek bones that just shows when the light catches. Benefit Watt's Up is a good one for a champagne glow.
There a lots of types of highlight, Benefit High Beam, Moon Beam and Sun Beam and all liquid form and then you have powder highlights such as MAC Mineralize Skinfinishes. Watt's Up is a cream to powder in stick form which you can use with a brush or place it straight onto the face and then use the buffer on the other end or your finger to blend it out.
The nicest thing about Watt's Up for me is the colour, it's a subtle champagne and looks pretty on all skintones. It's a sheen on the cheeks that looks pretty when the light hits it.
What's your favourite highlight?