From powder, to cream, to liquid. The shimmery goodness it my fav. I think it helps define features and makes your face look slimmer. It also makes you look very youthful.
I feel that it difficult to take a decent picture of clear highlighter but it looks awesome in person. My favourite product ever is the Benefit High Beam and I've only got a small sample from boots in the 4 minis for £15 deal. Then I love my No7 Instant Radiance Highlight stick for £9.95 with a highlighter powder to set the cream.
The following snapchat filter is basically the ultimate highlight that would be hard to create in real life.