The favorite insults I've ever received.
1) Comment from my high school english teacher (Advanced Comp? Perhaps) on a term paper:
"Mr. [Fishmonger], your hubris is exceeded only by your ignorance."
(I kid you not. What an asshole. But an excellent insult.)
2) Upon looking up across the lab bench to see a co-worker looking at me, I harshly asked "What are you looking at?". The response: "A rank amateur."
Please feel free to contribute your own candidates in the comments.