Eye Am Watching You

So there's something off about the new guy. You want to keep him on his toes, let him know that he can't be at home just yet. You want him to know that you'll be watching him.

The wonders of nonverbal communication make saying all this without wasting your breath possible. Just perform these three simple gestures:

1. Point to yourself: "I"

2. Point to your eyes, preferably using the backward "V" Sign: "AM WATCHING"

3. Point to your target: "YOU."

Details can vary from forgoing some of the steps (most often the first one, since technically you're pointing to yourself in step 2 anyway) to using different fingers when pointing at different things, but this is how you generally tell someone that Eye Am Watching You. Though generally a threatening gesture, it is known to have at times been used in a friendly or reassuring manner as well; communicating something to the effect of "I'll be seeing you", "I've got your back" or such. In sign language, the same gesture from one side of the face (not centered) translates as "see" or "I see you."

Examples of Eye Am Watching You include:

Comics

In the Tiny Titans/Little Archie crossover Robin speculates (correctly) that Mrs Grundy is married to Solomon Grundy. Later Solomon Grundy shows up and claims to have no idea what Robin is talking about regarding supervillainy. On his way out of the classroom he gestures at Robin angrily.

Film

One of the possum brothers gives Manny this in Ice Age 2 when they notice that he's growing interested in their "sister", Ellie.
Seen in War of the Worlds (latest version), with two soldiers.
Robert De Niro's character does this to Greg Focker in Meet the Parents and its sequels.
A thug does this in The SpongeBob SquarePants Movie during the "Baby Hunt".
Officer Devereaux Cloudy with a Chance of Meatballs does a funny variant of this trope:

Officer Devereaux: This contact lens represents you! And my eye represents my eye! (puts on contact lens) I've got my eye on you!

Live Action TV

Barney from How I Met Your Mother uses this gesture to encourage his friends to "focus on the prize." Which is usually casual sex and/or hijinks.
Shirley on Community does this when she and Annie are deputized to monitor April Fools' Day.
In Ned's Declassified School Survival Guide, Vice-Principal Crubbs does this to Ned from time to time.
Doakes does this to Dexter.
Mike Chang does this to Coach Shannon Beiste after his girlfriend Tina mentions Beiste's name at an...inappropriate moment. While completely ignoring the fact that if he hadn't told Tina about how some of the other boys were using Beiste to, erm, cool off, she would never have used the method herself and therefore never mentioned the name...sometimes Mike's not all that bright, really.
An episode of Saturday Night Live with Zachary Quinto promoting the new Star Trek had a Star Trek fan do this to him with his fingers in the Vulcan salute.

Theater

Edward gives this gesture to Bella in Twilight the Musical.

Video Games

Drebin in Metal Gear Solid 4 does a variation of this to Snake called "EYE HAVE YOU", which starts at the "eye" step, then he clenches a fist, then points to Snake.
In Office Jerk and Office Zombie, the Jerk and Zombie both do this as taunts. The Jerk does the standard version. The Zombie takes his right eye out, points at it, points at you, and then sticks the eye back in the socket.

Webcomics

The trope image comes from this Theater Hopper strip.
A young Doctor McNinja does this to Frans Rayner when the latter is getting laughed at by the ninja guild for his neckbeard. And in a later arc, in the Bad Future, to King Radical.

Western Animation

Katara did this in "The Blind Bandit" episode of Avatar: The Last Airbender to the bully earthbender students.
- She also did it to Jet in "Lake Laogai".
Chief Lin Bei Fong from The Legend of Korra does this to Korra. Korra does the same back, only with a funnier face.
- Apparently in the Avaverse, instead of using the index and middle fingers to point to their eyes, they use the index and pinky fingers, which somehow looks considerably more badass.
In Phineas and Ferb episode "No More Bunny Buisness", Perry the Platypus does this to Dennis the Bunny.

Other

The I'm watching you rage face, which is of the third phase of the motions.