The dog from Duck Hunt (Nes) hands down. Why must you laugh at me! Why?!? But really that dog is pretty annoying.

The Sword of Righteousness from Earthworm Jim. It never shuts up, it has no idea how to give Jim proper battle advice, and it is a complete douchebag. Also, it forces Jim to wear an absolutely god-awful Viking costume out in public, because it says that "THIS IS THE ONLY PROPER COSTUME FOR A TRUE HERO!!!"

http://www.watchcartoononline.com/earthworm-jim-episode-7-sword-of-righteousness

"Exploit his weaknesses! Summon the warrior within! FEEL the BURRN!!! DESTROY him, with his OWNNN EEVILL!!! LEAP, with your right, I mean your left, YOUR LEFT!" -Sword of Righteousness (Earthworm Jim)

I think the most annoying character ever is Daisy. Her voice in Mario Kart Wii is REALLY annoying.

Slippy from the Starfox games.

I think that it would either have to be Slippy, or Lester, from Lester the Unlikely for the Super Nintendo. Lester, just doesn't want to cooperate with your controls. He always seems to do the opposite of what you tell him to do. So frustrating! 

Since everyone said my instant first choice from when I read the title (lol @ the navi hate) I started to get flashbacks of Batman Arkham City and all the obnoxious henchmen who literally make me so mad I stop side questing just to rip apart a good group of 10 or so.  HEY BATMAN YOU SCARED? RUN YOU CHICKEN? and other classics, in an extremely obnoxious inflection, really make me want to beat someone down pretty bad, just on the premise of lack of creativity, lol, which these henchmen seem to run on like Dunkin Donuts.

Barathemos :
I have to agree with you in gold/silver V2 your mom is always spending your money and you are like MOM WHY 

Bianca from Pokemon Black and White and also Iris. 

Omochao from the Sonic series. He is this turtorial thing that has this annoying voice. 

Navi is quite annoy but the is another character in the Zelda series that grinds my gears harder!

I hate the Happy Mask Salesman!!!!

(the next paragraph contains a few mild spoilers to the Majoras Mask)

He starts off by stalking you and the skull kid until you get to the Clock Tower, where he forces you to get his beloved Majora's Mask back. When done he doesn't give you any award, like a medal or a certificate. I know it's pushy but I had to go on the moon to get that God Dam Mask back and then to be greeted by nothing but the End Game screen!!!

His character annoys me too. The laugh for starters is pretty creepy and he glitches around a lot. When I say a lot I mean there is no animation for him changing position! It hurts my eyes just watching him.

So that is who annoys me the most! Grr!

Lakitu in the side scrollers - he's so unpredictable and if you stop for just a second he's already dropped two Spinies in your general vicinity with a third on the way.

Lakitu in Mario Kart - "OK Dude, I know I'm going the wrong way. You're just making matters worse!"

THE stanking Frog in Starfox. Silppy. His voice and his constant call for help is why I'm putting him on the list. and on top of that he's not very useful either. I'd rather let him die.

Most people have probably already said this, but I'm going to post it anyway.  It has to be either Navi or Omochao, but I'm leaning more on Omochao.  He is literally everywhere in Sonic Adventure 2.  The only thing I like about him being in Sonic Adventure 2, is to pick him up and throw him off a cliff.  It really eases the anger inside me.

Iris from pokemon b/w/b2/w2. "You are such a little kid" seems like name calling to me. She is really annoying, and she easily gets on my nerves. She thinks she is special.

DittoDude44 : Iris is cool! The best protagonist from Pokemon! 

I would say Navi from Ocarina of Time. She just blurts out at you at the wrong times and you HAVE to talk to her to be able to use the C ^ button! "Hey! Listen! Hey, Listen!"

"What do you thinkk Saria would say if you told her you were saving Hyrule?" I already told her, so I'm pretty sure I know what her response would be. Navi is probably my least favorite character in anything, ever. Also, Groose at the beginning of Skyward Sword was really annoying. The first thing I wanted to do after I got my sword was kill him. Later on though, he became my favorite character in the game.

Oh I wanted to share my opinion so much about this.
So here is a top 3 annoying characters I ever met:

-3rd:Creepers
-Game: Minecraft
-Description: Do I need to describe it?Well they are annoying and explode in your face, and when you are mining and they just start exploding they are really annoying.

-2nd:Little enemies that jump on your face
-Game: Blood 2: The chosen, AvP games , Etc.
-Description: Ever met something that jumps on your face? Well there are these little ******* that scare the **** out of you when you least expect to and you don't see because they are so small, I HATE THEM.

-1st:Every mutant in STALKER Misery mod 2.0
-Game: S.T.A.L.K.E.R. Call of Pripyat(Misery 2.0)
-Description: I never met something more annoying than the mutants. Have you seen a dog in that game? It kills you in 3 bites, and they also come in packs. Have you ever seen the Bloodsuckers? Oh they are invisible and they can kill in 2 hits? Well how about the Controller? He literally kills you from the other side of the map in 2 hits(that might be a bug).There are also Zombies with guns, Chimeras that are hard to kill, they incredibly powerful and fast snorks, the Pseudogiant that kills in one hit while charging at you. And the one I had most problems with...The burer, they kill you just by looking at you.

It's either Navi or Omochao. Ironically enough, both of them try to "help" the player by giving them "useful facts".

Now I agree Navi is super annoying.

But the character I most dislike is Chuchu from Xenogears.
She is useless even though you can have her in your party she is the weakest character and even when not in your party she stalks you!!!  She's too cute and too scary plus useless!