Every great horror movie should have that cryptic stranger who knows whats going on. That guy that in the beginning hints of things to come. That guy who screams 'You're Doomed!' at the cast of cannon fodder.
I love that guy. I've secretly always wished that I was that guy. Anyway, Its my birthday, the last thing I usually write is actually the intro. So I'm not going to waste much more time. So here is my top five, un edited (so ignore the glaring errors of grammar((lol))) Here is my top five “You're Doomed!” guys.

Ripley – Aliens

Most 'You're Doomed' guys are minor characters, who make only a momentary appearance. They get in, lament about how fucked you're going to be, and get out. Its their job to act as a trailer for things to come. You have no idea who they are, or how they know what they know. The only thing you can be sure of, is that they're right.
None of that applies for Ripley, cause not only is she the 'You're Doomed' guy of 'Aliens', she's also the main character.

In the first movie we see the crew of the Nostromo systematical killed off by the Xenomorph (The Alien of 'Alien')... Now I'm going to avoid spoilers for most of these movies, but I don't think that saying Ripley survives 'Alien' is a spoiler, since... well, there was four sequels starring her.
At the start of 'Aliens' (The sequel is just a multiple of the first), we hear Ripley giving a few speeches about how the Xenomorph is super dangerous, and that it should be avoided at all cost! You'd be mad to go anywhere near it!
She then goes on to ignore her own warning and proceeds to go straight for it! Now, I know there was more to it. But, this is a very unique duality to the character, she fills not only the role of the warner, but also the dumb ass that ignores the warning!

Ol' Judd – Pet Semetery

The best 'You're Doomed' guy is usually, old, and wise, with knowledge of a dark past, that is bound to repeat itself.
O'l Judd of 'Pet Semetery' (intentionally spelt wrong), is exactly that. Except... that dark past he knows about? That wouldn't have actually repeated itself if he had just kept his old hick mouth shut. But you know how the elderly are, they just like to have someone to talk to.
Judd blabbers about the mystic Indian burial ground to his neighbour Lou, and they even bury Chruch their cat there. The results are a psycho zombie kitty! Lou asks, “Has anyone ever buried a person up there?”
O'l Judd expands on the story, telling him, “Some times, dead is better.” But this warning, again, would not of been needed, if O'l Judd had just shut the fuck up! Why blabber about the evil, Native American, burial ground, in your back yard? Old people that talk like that get put in the home! Way to drop the ball Judd.

I didn't want to spoil the movie, even though its been out for years. So instead of a clip of Judd I have the Music Video for the film. I haven't watched it, so I'm just assuming the video is spoiler free...

Randy – Scream

The first 'Scream' is not only is a great slasher movie, but its also a top notch comedy. Mostly since every single character in the movie is aware of the conventions of slasher movies. Especially, Randy, who may not be old, but he is defiantly wise beyond his years... well at least, wise beyond his own movie.
Randy sets up the 'rules' of the genre, for everyone. Which essentially is a serial killer check list.

Had loads of sex? Your dead.
Drink and/or do drugs? Your dead.
Say you'll be back? Your dead.

The rules of the slasher movie are put in place because slashers are supposed to be fun, we don't want to see people we LIKE be mutilated, that’s no fun. So bullies, drug addicts, and fornicaters are the targets. Are those people evil, and deserving of death? No. But they go against social norms.
Slasher movies are extremely conservative for that reason... I mean, yes, the Friday the 13th movies showed a lot of boobs, which seems liberal. But this liberal behaviour is always met with death, and Randy makes sure we know this.

See that? Randy is so on the ball, his mind so far out of his own movie, and thus beyond his own existence, he even implicates himself as murderer.

Addie – American Horror Story

When I heard that the guys from 'Glee' were doing a horror themed TV show, my first thought was the choreographed 'Thriller' zombies, wearing clothing from the Gap, in a school club run by their third period Spanish teacher.
What we got instead was just as awesome, 'American Horror Story', featuring the finest actress with down syndrome, I've ever seen, Jamie Brewer. She plays Addie, the 'You're Doomed' guy of 'American Horror Story'.

Most 'You're Doomed' guys, either scream at you about how you're going to die, like a mad man, or give long winded speeches, Addie keeps her shit simple.

“You're going to die in there.”

That's it, that's all she gives you. And its creepy as fuck. She says this a few times, offering up no more info then that. Just plain and simple. 'You're going to die in there,' no idea HOW, but its certain to happen.