I like using funny expressions, and here are just a few that I use:
"oh, take a pill" (chill out)
"I'd rather chew glass" - pretty self-explanatory
"are you thick?" (are you a dunderhead?)
lame-o
I have more, but I cannot dredge them up at the moment. I really like the expressions from Yorkshire, Scotland, Victorian England...
PS: Edited to add:
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ok, here are two more:
"What does that have to do with the price of tea in China?"
and
"He has a problem with his elbow."
(means he has a drinking problem. I came across this expression exactly one time in my life, it was in a book written by a Maritimer [a person from one of the Maritime provinces in Canada: New Brunswick in this case.] He explained that it was a Maritimes expression.)