The Kubrick Stare

"In that showdown, and at several other times in the film, Kubrick indulges his favorite closeup, a shot of a man glowering up at the camera from beneath lowered brows. This was the trademark visual in A Clockwork Orange, and Jack Nicholson practiced it in The Shining. 

What does it mean? 

That Kubrick thinks it's an interesting angle from which to shoot the face, I think."

— Roger Ebert, review of Full Metal Jacket

The Kubrick Stare is really quite simple to pull off. You simply do the following:

1. Tilt head down
2. Look up beneath eyebrows

...and voila! Instant super-creepy look!

It generally signifies that the character in question is either really, really pissed or really, really deranged, and the person they're looking at is really, really screwed. Other times—usually when combined with a smile—it means they're feeling really, really clever (regardless of whether or not they actually are).

When a show or film utilizes the look, it's often a homage to Stanley Kubrick.

Either way, it's really creepy and ominous. Although depending on the context, it can also be very badass.

Often accompanied by Creepy Shadowed Undereyes, Red Eyes, Take Warning, a Psychotic Smirk or a Slasher Smile, and also a reveal matched with Scary Shiny Glasses. If a character combines this with Finger-Tenting, odds are, he's a Magnificent Bastard. 

Heroic examples often are used for Staring Down Cthulhu. 

See also: Hidden Eyes, Death Glare, and Disapproving Look. 

Compare Primal Stance and Limp and Livid.