The one that sticks in my head with my 1st pregnancy was "oh yes, I had guessed - you've looked awful for months". That was nearly 11 years ago now and I still remember the horror I felt - I was horrendously sick with all my pregnancies but I had tried so hard to hide it and I just felt like a total failure at that point.
With my 2nd I don't think I got anything particularly negative, but with my 3rd all hell broke loose! My 3rd turned out to be 3&4 and yes, it was a shock, but once we got over the initial shock of it we were OK and we were happy about it. I got every negative thing you could possible think of said to me, as well as a lot of very personal questions from complete strangers...
"Was it a natural conception?"
"Do you have twins in your family?" (My answer: no) "oh dear, so you really have no clue how bad this is going to be then"
"How on earth will you cope?"
"Your life is going to be awful!"
etc... etc...
I think the 2 that stick out more than any though were...
"oh my goodness! You're going to be huge!" followed by loud laughter. No congratulations, no nothing - just a horrified comment about how big I was going to be! (I wasn't actually and I wish I was still in contact with that ridiculously shallow person at the end of my pregnancy when I walked into the hospital in my own jeans!)
"That is the best contraceptive advice I have ever heard" - this actually came from a very good friend, who only has 1 child and this probably hurt me more than anything else. I know that the idea of twins does put some people off trying for a 2nd or a 3rd, but it was just so hurtful and I've never forgotten it.