The most notable characteristic of Dead Space protagonist Isaac Clarke, besides the glow-in-the-dark welding suit he wears, is his silence. He doesn't speak at all throughout the entire game (unless you count pained grunts as speech). Isaac wasn't always this way, though.
Scene One: C.E.C. Base, Medical Bay
KENDRA DANIELS: How does the suit feel?
ISAAC CLARKE: It's kinda digging into my back.
KENDRA: Oh, that's the health indicator you're feeling. All the environmental suits have them now.
ISAAC: The what?
KENDRA: (she pulls him over to a mirror) Look. You see that long light on your back? That's a visual display of your health. The light gets shorter as your health deteriorates. Handy, huh?
ISAAC: (looking over his shoulder at the mirror) How am I supposed to see it?
KENDRA: What do you mean?
ISAAC: It's on the middle of my back. Couldn't you put it on the wrist or something?
KENDRA: Wouldn't work. The hologram for your inventory pops up on your wrist.
ISAAC: Inventory hologram?
KENDRA: (nods) It shows everything in your bags.
ISAAC: Why wouldn't I just look in my bags to find that out?
KENDRA: There's a meter on your back for stasis module energy, too!
ISAAC: (pause) Other than that, the suit feels fine.
Scene Two: C.E.C. Base, Briefing Room
GENERAL XAVIER: ...So we'll be sending in the five of you to investigate the ship.
ISAAC: Excuse me, sir?
ISAAC: You're only sending five of us? Isn't the Ishimura a massive ship?
XAVIER: Only five? Isaac, we're a galactic, multitrillion dollar corporation. We can't throw a half-dozen people at every massive, ludicrously profitable mining ship that mysteriously loses contact for no apparent cause!
ISAAC: Does that happen often?
XAVIER: It just happened!
ZACH HAMMOND: What are you so worried about, Isaac? We're taking a gun with us! That'll be more than enough to fend off whatever sinister forces have managed to commandeer a ship staffed by several thousand people!
ISAAC: (slams down the face plate of his helmet, crosses his arms)
Scene Three: USG Ishimura
KENDRA: (via hologram) Great job, Isaac! you fixed the engines!
HAMMOND: (also via hologram) Looks like the life support's on the fritz now, though.
KENDRA: Bunch of asteroids hurtling toward the ship, too.
HAMMOND: We'd better get on that.
ISAAC: Alright, well I can go fix the life support, can you two -
KENDRA: We're busy.
HAMMOND: Totally busy.
KENDRA: I'm checking something on the computer here. No time to stop asteroids.
HAMMOND: I'm checking something of equal importance on another computer far, far away from whatever section you need to get to in order to shoot down the asteroids.
ISAAC: The bridge?
HAMMOND: Yes. Every door between me and the bridge is locked. Locked forever.
KENDRA: You don't mind doing both things, right Isaac?
ISAAC: (anguished sigh, walks off into the bowels of the Necromorph-infested ship)
KENDRA and HAMMOND: Score!