I am very fond of this comment: "Economists exist in order to make astrologers look good."
Some of my favorites for Mathematicians:
"Proof is trivial"
"It is clear that ..."
"It can be easily shown"
And here is one from a math text:
"I never came across one of Laplace's 'Thus it plainly appears' without feeling sure that I have hours of hard work before me to fill up the chasm and find out and show how it plainly appears".