I *finally* perfected the art of not talking to myself out loud, but I frequently do it inside my head. For instance:

-"For God's sake, how hard is it to jump on a goomba three times without getting killed?!" (Playing New Super Mario Bros. on DS).

-"Where is the last f***ing crystal?? Am I meant to go back and shoot that last tree demon or what?" (Playing Hocus Pocus on my ancient Toshiba laptop that only comes out when I feel like playing that particular game).

-"Oh God, don't say that stupid dog buried the TV remote as well... I mean, I can live without the stereo remote, but I have no idea how you're meant to use Sky TV without a remote..." (Myself, about the TV remote. By the way, the dog didn't bury it, my sister hid it).

OMG, I thought I was the only one with that weird problem (or not problem)

Don't worry, be mad is not so bad...

^ That happens to me too. I guess I talk to my conscience (is that how you spell it??) rather than having two personalities, but I'm still beginning to think I'm fairly insane.

^haha, don't worry... maybe we are sane and the rest people are insane...

I have ACTUAL conversations with myself.
It goes along the lines of:
ME 1: What shall I do... homework?
Me 2: Hmm. No.
Me 1: It needs to be done.
Me 2: It needs to be done tomorrow. Go on sims.
Me 1: Which sims? Sims 3, sims castaways?
Me 3 (*sigh*) : Or Harry Potter.
Me 1: Harry Potter!
Me 2: Harry Potter!
Me 3: Harry Potter!

^ Same here, only it sorta goes along the lines of:

Me 1: So, I have about a ton of homework this week
Me 2: Geography homework, then?
Me 1: That's not in until Thursday
Me 2: Today is Tuesday
Me 1: So?
Me 2: Fine, do it tomorrow. Maths homework?
Me 1: Um no, I was planning on making up an excuse to get out of that, remember?
Me 2: I keep telling you not to do that anymore...
Me 1: You're not the boss of me!!!

So yeah... Then my teachers wonder why nothing gets done...

^I do that too, all the time. Only it usually goes on in my head.

Me 1: I really want to play Soul Calibur right now.
Me 2: You can't. Your neighbor's coming over to do that bible thing.
Me 1: Ugh. Stupid bible thing
Me 3: Hope she leaves early.
Me 1: Or, if I'm lucky, she'll want to play Soul Calibur!
Me 2: Good idea...
Me 3: She's coming over in half an hour!
Me 1: Ok, ok, I get what you're saying.
Me 3: Hurry! Play! Play!

Me 1: What can I do?
Me 2: Homework
Me 1: What homework?
Me 2: Don't you have homework?
Me 1: No... I think...
Me 2: Why "I think"?
Me 1: I don't know where I wrote the homeworks
Me 2: Why not?
Me 1: Because I think I wrote them in my hand... And I washed it... *looks down*
Me 2: WHAT?? Can you be more Stupid!!!!!!!!!????????
Me 1: Sorry...
Me 2: Every day it's the same!!
Me 1: Sorry!!
Me 2: No! I won't forgive you!! You said you will study more...
Me 1: *looks down again*
Me 2: wait... Why aren't you studying???!!!
Me 1: I... I... sorry...
Me 2: Study!!
Me 1: If I study you will have to study too!!
Me 2: Don't yell at me!!!!
Me 1: Forgive me...
Me 2: No.
Me 1: Please...?
Me 2: Ok... I will have to live with you forever so...

Hahaha, we're all going crazy.

Being crazy is what makes us sane.
...
Hey, do you think that'd make a good signature? Hmm...
My latest conversation with myself, while playing Hocus Pocus:

Me 1: If I fail again this time I'll do my Geography homework. OK?
Me 2: You said that last time, and then you got trapped in the lava and died, then the time before when you had to re-start the level because you fell off the elevator thing, and the time before when something weird happened, and...
Me 1: OK, I get the point. What I MEANT to say was I'm going to keep doing this until I finish or lose my mind, whichever comes first, and I'm not going to do the Geography thing until the last day of the Easter holidays.
Me 2: Thought so. You're so irresponsible...
Me 1: So are you, we're the same person, remember?
Me 2: No, YOU'RE the person, and I'm your conscience.
Me 1: Isn't a conscience meant to direct you to do the right thing, not BOSS YOU AROUND ALL THE TIME???!!!!

So yeah. As usual I end up rebelling against my conscience. Bleh.

The amount of times I have.
If I had a PS3 microphone, my opponents would get so narked at me being all:
"GODFUCKINGDAMNIT REVERSEEEEEE. I'M PRESSING R2, REVERSEEEEE. STUPID FUCKING LAGGING, REVERSE YOU BLOODY FOOL. REVERSE NOWWWWW!"
And I have a tendency to sing along to entrance music too... very loudly. And I really REALLY can't sing.

Then there's when I'm at school. If I'm doing anything on the computer, I'm always all:
"ARGH. WORK. DON'T CRASH ON ME FOOL, OR YOU GONNA GET SOME BLOODY NUTS IN YOUR BLOODY CD DRIVE AND YOU'LL BLOODY CRASH THEN UNTIL YOU'RE DEAD AND... Hi, Miss"

And then there's when I'm watching TV/a film. I give myself a running commentary. >:I
I'm all:
"NO. DON'T DOOO THAT. THAT'S NOT THE ANSWER!!!!"
or:
"GROW SOME EYEBROWWSSSSSSSSSSSSS!"
or:
"LOOK BEHIND YOU, JAMIE KENNEDY. NO, DON'T KILL HIM. OH FUCK YOU, MRS LUMAS, FUCK YOU. HE WAS THE BEST CHARACTER!!!!!!!"
or:
"OMGOMGOMGOMGOMG DO'NT KILL SURESH. OH THANK GOD, I LOVE YOU HIRO."
or:
"GET A ROOOOOOOOOOOM!"

...
Well, you get the idea with that.

TIRA. WHAT HAST THOU DONE WITH HER?
Speaking of people who talk to themselves, of course. xD

^Yeah...
Well, uh, I changed my av cuz people *coughminusandtorakocough* were nagging me about it. I'll probably alternate between the two, tho.

DO NOT SUBMIT TO PEER PRESSURE.
Which part of school did you not pay attention to? >:I

Me 1: Uummm... this band isn't really good... Do you like it?
Me 2: Uummm... Not bad
Me 1: Really do you like it?
Me 2: Well... wait!! that song is... AWFUL!!!! Argg!!! Change it!!!
Me 1: But this is the best song from this group!!
Me 2: OMG, it's a shit!!
Me 1: Did you really listen to the others? ¬¬
Me 2: Yeah, it's true. This band is a shit...
Me 1: Try another?
Me 2: Oh! This song is much better!
Me 1: Yeah, but the videoclip scares me!!
Me 2: What are you saying?? I love that doll-guy!!
http://www.youtube.com/watch?v=RNtGYdm2rOY
Me 1: umm... yeah... You are a little weird, right?
Me 2: Yes, why?
Me 1: ok... another band?
Me 2: Oh, no, please!! Not bad but very boooooooooooring
Me 1: This?
Me 2: This really great!!
Me 1: How can't you be angry with me?
Me 2: Why?
Me 1: You... You hated me...
Me 2: Umm... sometimes... But it's nice to talk with you ^.^
Me 1: ^.^
Me 2: You are always there to talk to me!
Me 1: Obviously... -.-

I just got back from a school camp and am crazy with tiredness, so I'm talking to myself a bit, and was on the bus back.. (4 and a half hours in a bus is NOT FUN)

Me 1: Oh my God *nameremoved* keeps staring at me. That's weird.
Me 2: Maybe it's because you're staring at HIM?
Me 1: No, he's looking at Adelle. Of course he is.
Me 2: Admit it, you think he's cute.
Me 1: SHUTUPSHUTUPSHUTUPSHUTUP.

I can't count how many times I told myself to shut up in the past four days...

I have Soulblade, the original. And I end up screaming and shouting at it in the last two rounds, where you have to fight Cervantes as a stupid pirate, and then as a stupid skeleton. Why? I don't know.
Anyway. I usually end up all:

"STOP CHEATING. YOUR SWORDS CAN BLOODY FLY, THAT DOESN'T YOU HAVE TO DO THAT AND CHEATTTTTT."
And sometimes I get very nasty and I'm all:
"YOU OLD UGLY GRUMP, GO GET BACK IN YOUR BLOODY BOAT."

You should see me playing Tekken 5. (Not so much in Tekken 6 for some reason...)
"YOU CAN SHOOT FIRE... OUT OF YOUR STOMACH? CHEATERRRRRRRRR!"

In Tekken 6, I'm just all:
"BLOODY DAMN YOU, HEIHACHI. YOUR STUPID LEVEL DOESN'T DROP ENOUGH HEALTH. MY PARTNER IS UNCONCIOUS AND IF I TRY TO SAVE THEM, I'LL- BOLLOCKS, I'M DEAD! JUST BLOODY WONDERFUL! NOW I HAVE TO WATCH YOUR STUPID CUTSCENE AGAIN!"

I get very angry online aswell, even though they can't hear me.