Definitely eyes... anda can tell something (practically everything) when anda stare at someone's eyes. anda can also tell if they're lying atau not. anda can tell what they are feeling at the moment when anda look right into their eyes. Unless you're clueless, of course...
The eyes, just because anda can tell how someone feels atau what personality they have (sometimes, personality isn't always that easy to decode) just sejak looking into their eyes. Especially because when I see a person atau creature that makes me sad atau scared, it's almost always because of the look in their eyes.