I think all the voices in K2 suck lol.  Great game though.

My pick is zombie noises from Left 4 Dead, gets real old real quick. Oh and the stupid witch moan also.

I didn't think Algretto and Chopin were as bad, but Beat was bloody annoying

They didn't make my ears bleed, I'll give them that much...

 I agree with you here,  I killed that SOB so many times cause I was tired of his voice

the announcer in Unreal Tournament 2004 saying "denied!" when a ur deemer gets stopped. Its not him thats annoying, its the fact that you associate that voice with absolute failure : (

Old School:

Berserk (Atari) - the laser sound. Almost every Atari game's laser sound is annoying.

Current Gen:

Lymle - "kay"

Every sound effect in Civil War: Secret Missions.  At least minus the somewhat decent voice actors, but the sound effects are horrid.
http://www.youtube.com/watch?v=6sA1o_7wbbE

The Screamer from The House of the Dead: Overkill is very unnerving every time she... screams.

Other than that, health sirens are pretty annoying. Yes, I know I'm low on health Mr. Video Game, but I can't do anything about it! Gah!

Oh shit, I totally forgot about that.

That's the Star Ocean 4 girl, right?

I take back what I just said earlier, I was most definitely not OK with that, and I only ever saw it from one of the cutscenes posted as a Youtube video.

The belching sound the patients made in Silent Hill 4.