The chaos quotes are great. Particularly the cultists.

"Aaah, my spleen!"
"Crush, kill, haa haa, destroy!"
"Grant us the gift of the chaos gods, great one!" 
"DO YOU HEAR THE VOICES TOO?!"
"I feel the warp overtaking me... it is a good pain!"
"Sanity is for the weak!"
"It is as though a thousand mouths cry out in pain."
"Enemies! We need enemies!"
"Maim, kill, burn! MAIM, KILL, BURN!"
"Rend them in half!"
"I feel the maw of despair swallowing me!"
I am not your bootlick!"
"Blood, blood, blood, blood!"
"I drink their blood from their hearts!"
"Split them open!"
"Uuuaaarrarraaargh!"
"Kill! KILL!"
"For the slaughter!"
"Why aren't we killing yet!?"
"I will shatter their souls!"

And my personal favorite:

"Hwee haf captoored eet foar KAYOSS!"

When Duke Nukem says "I've got balls of steel"

It's hawt.

Zero-Wing, chinese game that failed at grammar, also where the meme "All Your Base Belongs To Us" comes from, I love this scene in it, makes no sense at all but is funny as shit.

http://www.youtube.com/watch?v=FVsijmCFs50

pong

Any sound in Bad Company 2. Particularly when you headshot someone at very close range with a shotgun and the pellets hit the helmet. CLANGGGGGGGG.

Now that i think about it, this is so true, and sooo satisfying

Halo series when you kill an elite he falls to the ground yellin "wort wort wort" and grunts screamin AHHH Leader killed run awawy!!!!!!! so awsome...

Super shotgun from Quake 2. Basically the best fucking shotgun sound ever conceived. The sound can easily be duplicated with words: BOOM-chk-chk. And it's a big fucking BOOM that satisfies every cell in my body. Also, the railgun from the same game. Very characteristic and recognizable, as well as plain awesome. Hearing that sound at the same time as a supersonic slug blasts through a stroggs chest leaving that nice helix behind made it all the more enjoyable.

Oh yeah, Supreme Commander 2 has excellent sounds if you ask me. Especially the firing/impact sounds.

Metal Slug.

The noise a Chain Chomp makes. :O