William Shakespeare has to be the Grand Master of Insults. Really. How many people do you know who can talk smack with such finesse as:
More of your conversation would infect my brain.
There is no more mercy in him than there is milk in a male tiger.
-and how about this one-
Thou sodden-witted lord! Thou hast no more brain than I have in mine elbows.
Here is a link to Buzzfeed, showing seventeen Shakespearean insults…featuring cats! It doesn't get any better than that. Buzzfeed Shakespearean Insults
As both a reader and a writer, I appreciate the nuances of insulting someone without having to resort to cussing all the time. The Bard shows us how creative words can truly be.
Here's a link to a Shakespeare Insult Kit. You start with "Thou" and pick one word from each column to create a unique insult, like "Thou goatish, milk-livered, canker-blossom." Or use your own words to make something up and give me a sentence in the comments. Maybe I'll even use one of your creations in an upcoming novel!