If you ever want to tell someone EXACTLY what you think of them, but find yourself lost for words, you could do worse than quote the Bard and here are a few suitably poisonous insults that are possibly worth committing to memory:
That kiss is as comfortless as frozen water to a starved snake.
- Titus Andronicus
There is no more faith in thee than in a stewed prune.
- Henry IV, Part I
The tartness of his face sours ripe grapes.
You are like the painting of a sorrow, a face without a heart.
I was searching for a fool when I found you.
- As You Like It
Thou hast no more brain than I have in mine elbows.
- Troilus and Cressida
You are not worth the dust which the rude wind blows in your face.
- King Lear
Thou art unfit for any place but hell.
- Richard III