Highlighter around your eyes can do a lot to open up your face, but the best placement might not be exactly where you'd think. Instead of putting a luminizer directly under your eyes, you'll get more bang for your metaphorical buck by blending a highlighter like Guerlain Météorites Powder For The Face onto the inner corners of your eyes using a small eyeshadow brush. It'll make them look wider and brighter without having smoky eye-level drama.
Your brow bone is the other choice spot for illumination, since it lifts the eye and makes the entire area look less “heavy' (or, you know, tired). You can go a little bit crazier with the highlighter here—try a liquid formula like Benefit High Beam or Givenchy Mister Radiant.