Here, I'll start. An unhappy follower of Pelor might declare 'sunburns and starvation!'
And of course, 'by Khorne's brass balls.'
The worst insult you can give a dragon is to call it a "worm", emphasizing you are not in fact using the draconic honorific of "wyrm".
Call a black dragon 3/5 of a dragon if you want to be cheeky.
"Your Father was a Gecko and your Mother was a spell component" -Kobold.
knife ear - elf
Boots - dragonborn
Anything with demonic annotations - tiefling or drow
Any halfrace (half elf or half orc) - halfbreed or Mixed or something like that.
Your momma so fat she use a bag of holding as panties
Dwarves are filthy diggers