The most annoying expressions...

I suppose for me it isn't really what is being said, it's who is saying it.  Some things I find a bit irritating to hear, but if I like the person, then it really just doesn't bother me. If I don't like them, or their manner (if I don't know them) then I find a good many things annoying. 

Now that I think of it, there is generally little reason to use the word "literally" in its correct sense.

When you say "literally", you are saying that what you are saying is true. And it is usually assumed that what you are saying is true anyway.

For example:

That made me laugh so hard I fell on the floor.
That made me laugh so hard I literally fell on the floor.

They mean the exact same thing.

I agree with you on "obviously," but for me you've just given an example of exactly when "literally" should be used.

If I heard the first I wouldn't assume you really fell on the floor, just that you laughed a lot and were using a bit of hyperbole for affect.  I think you do need the "literally" to covey that you really did fall on the floor.

There are plenty of idioms like this in English, e.g. "that weighs a tonne" usually just means something is heavy, but every now and then things do literally weight 1000Kg.

If I heard the first I wouldn't assume you really fell on the floor, just that you laughed a lot and were using a bit of hyperbole for affect.  I think you do need the "literally" to covey that you really did fall on the floor.

Which begs the question: Do people really laugh so hard that they fall onto the floor?!? I don't think I ever have.

I'm going to throw "pressurized" into the fray.  Although "irregardless" makes my list as well. 

This gets on my nerves so very badly I have a whole rant built up around it.  People are not pressurized into doing things, they are pressured.  Vacuum-sealed things and pressure-cookers are pressurized, not people.   

Also "obviously" usually makes you sound condescending and/or closed-minded and doesn't really add value to the conversation.

I completely forgot about the word "obviously".  I HATE, HATE, HATE that word!!

My hubby is British and would always use it more in arguments.  It got to the point I had to ask him to refrain from using the word at all because it means precisely what you've said:  "You're an idiot."  I've been hearing the word used so much since moving here.  It seems very ingrained in many people's vocabulary.

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I'm one of those who says "Fixing to..."  I'm from Texas so I kind of can't help it!

The expression 'oh snap' has been grating on my nerves for a while now. I love teens, and usually their expressions make me chuckle, but this one's been around for a while now and it's just 'old'.

I also hate it when people say "SHUT UP!" in disbelief.  I am so offended by that, even if it's meant in a passive way. I also hate it when people "joke" and call you a loser.

"Hey Loser...did you ever find your car keys?"

Any derogatory remark said in a "joking" way is not amusing to me.

I am afraid that if we move to England, that when we eventually come back (or are there for awhile) I will be terribly made fun of by family and friends for being "pretentious".
Look at how badly Madonna is criticized for "posing" as a Brit. I mean, if you live in a foreign country you are bound to pick up accents and vocabulary but Americans seem to have a real problem with that.
I know my brother, for one would be the first one to make fun of me for being pretentious if I happened to say "lift" or "loo" or whatever!

I also hate it when people say "SHUT UP!" in disbelief.  I am so offended by that, even if it's meant in a passive way. I also hate it when people "joke" and call you a loser.

"Hey Loser...did you ever find your car keys?"

Or this one " hey fool...blah, blah, blah" or 'dude'..preceding any conversation. My teenager has a friend that used to address me as 'Hey Mrs.T, dude...'

Now that I think of it, there is generally little reason to use the word "literally" in its correct sense.

When you say "literally", you are saying that what you are saying is true. And it is usually assumed that what you are saying is true anyway.

That depends though

you could say "I pissed myself laughing" - when you wouldn't actually have wet yourself but it's a saying to describe how funny something was.
But what if you really did wet yourself? And I've heard someone mention this "I literally pissed myself laughing" and when questioned, they really did!

I remembered one of the expressions I hate. "touché" it suddenly became popular to say not too long ago and now everyone says it!

I am afraid that if we move to England, that when we eventually come back (or are there for awhile) I will be terribly made fun of by family and friends for being "pretentious".
Look at how badly Madonna is criticized for "posing" as a Brit. I mean, if you live in a foreign country you are bound to pick up accents and vocabulary but Americans seem to have a real problem with that.
I know my brother, for one would be the first one to make fun of me for being pretentious if I happened to say "lift" or "loo" or whatever!

Wasn't Madonna crticised for having an English accent after living here for about two months?

I think its quite natural to pick up a bit of a dialect after living here for awhile, but I doubt that most people will ever aquire a "full" accent (unless they move here when they are children). 

DH's aunt living in the US for forty years (moved from Scotland when she was 20 or so) and while I can tell her accent is a bit watered down, she still sounds very Scottish.

Anyway, Its probably been mentioned in this thread already, but it really grates me when people say "I could care less".  The phrase is I COULDN'T CARE LESS!!!

I hate it when people use catch phrases from movies or TV shows. Would it kill them to show some originality?!? If I hear, "I'm not bovvered," or "I'm a laaady!" one more time, I'll scream.

Another one!

It drives me nuts when people say 'a tad bit' .. (as in 'a tad bit too small' or 'a tad bit over the top'.)

It's either 'a tad' or 'a bit'... it's NOT 'a tad bit'.

I hate it when people use catch phrases from movies or TV shows. Would it kill them to show some originality?!? If I hear, "I'm not bovvered," or "I'm a laaady!" one more time, I'll scream.

Hmm.  I'm a tad bit (heehee!) guilty of that, although not those two particular phrases.  I do tend to keep it at home and not use them in everyday conversations, so it's only obnoxious to my family.  I hope.

I hate it when people use catch phrases from movies or TV shows. Would it kill them to show some originality?!? If I hear, "I'm not bovvered," or "I'm a laaady!" one more time, I'll scream.

I don't use those two in particular, but lately whenever we hear someone on TV who mumbles or who we don't understand and one of us says "what did he say?" the other inevitably responds "something about curry."