[Luis Dias]

The Cube.

[Colonol Dekker]

Companion?

[Thaeris]

I'd also note other monsters from RPGs which aren't so much visually scary as they are freaky to deal with. For which purpose, the spectre from Avernum is a nasty, nasty dead chap/ess. The voracious ripping and tearing is something to be reckoned with....

[Commander Zane]

Giygas?

[T-LoW]

Giygas?

THAT dude freaked the hell out of me. Especially the awesome music during the battle against him.

[PsychoLandlord]

Giygas is the nuclear option of scary game enemies. He's not even capable of being in the contest - it's like when someone asks who the most powerful superhero is and some kid calls out Chuck Norris or Superman or some other infallible entity. It's not fair to the other guys in the running.

That said, Giygas is horrifying as all hell.

[FireSpawn]

So you want scary huh? Well here's some that when I met them, bricks were shat:

AvP Facehuggers: Bearing in mind that I was but a small child when I first saw Alien and Aliens (the medlab scene still haunts my dreams), and that in itself left a 'OMFG MOTION ON MY SENSOR, BURN EVERYTHING' reaction.

Any and ALL ghosts from Project Zero (Fatal frame): Sinister teleporting dead kids, 'nuff said.

SA-X: From Metroid fusion. Those moments stuck in that vent, waiting for her to leave the corridor, took days off my life.

The guy at the desk in Leasure suit Larry:...
 
The Arrogant Man/The Prince/Cabadath: From the Chzo mythos (mainly Trilby's notes).

Transcendent: *Whimper*

The ***** from Dead Space 2: Sudden and intense QTEs are NOT my forte.

Dekker: Especially when equipped with a maxim or in RTS's as an ally with teamlock turned off.

I know there are a couple of others, but I seem to have repressed them too deeply so I'll just sit over in this nice, safe corner and cower from all the remembered terror. 

[Colonol Dekker]

Cabadeth.




Project Zero.





Me?.....on multi?.....................with MadZims?

[Icewater]

Sup.

[Mikes]

The Aliens from the original AvP. Nothing else ever came even close. (Even the sequels didn't get them nearly as scary as the first part!)

[Colonol Dekker]

I hate hard Starcraft  skirmish Zerg AI..................

[Thaeris]

OHGOD.

Brood War custom map AI...

[headdie]

OHGOD.

Brood War custom map AI...

Me and my mates got creamed by the AI sooooo many times

[Thaeris]

It does make comp-stomps fun, though...

I think of playing on Battle.net, getting some chaps on board for a fight, having them wonder why I was rushing so much to get a defense up, only to be owned by the AI a few moments later.

[headdie]

having half the screen filled with zerglings in the first few mins of the game is more than a little humbling

[FireSpawn]

Dekker- Master of the: Tank rush, zergling rush, XV15 stealthsuit rush, K-Bot rush, Magha rush, nuke rush, etc etc.
If it can be built and it moves, chances are he's rushed (and destroyed) me with them.

[Luis Dias]

http://www.youtube.com/watch?v=GQBt6uxjwsI

[Hades]

Dekker- Master of the: Tank rush, zergling rush, XV15 stealthsuit rush, K-Bot rush, Magha rush, nuke rush, etc etc.
If it can be built and it moves, chances are he's rushed (and destroyed) me with them.

Doesn't mean he's a master. It could mean that you just suck.

[FireSpawn]

Doesn't mean he's a master. It could mean that you just suck.

I'll have you know that I'm a tactical genius...once I reach top tech level and start spamming the special units.

Don't judge me!

[Admiral LSD]

Also, cloaked Drillers from the first Descent. Other bots were capable of being scary, but hearing a whine of a Driller and not seeing one could be the scariest thing in the entire game.

Heh, I was going to mention some Descent stuff myself.  Drillers were pretty scary as a whole, but the cloaked versions were doubly so.  And those Fusion Hulks...I have that sound they make seared into my brain.  The Old Scratch in D3 was pretty scary in its own right.

Fusion Hulks had the most awesome sound.
Red Hulks were like OHSHI---

That sound the Fusion Hulks made was pretty cool, but their speed and rate of fire meant they weren't even close to matching the level of scary of the Drillers. Get a couple of them in a room and half your shields would be gone before you had time to crap your pants after hearing that telltale whine. Red Hulks were pretty bad too, especially in narrow tunnels. It was hard enough dodging a homer as it was, having nowhere to run was just OH****!