As sharp as the wife's tongue (Not mine you understand)
Sharper than a guardmans creases
Sharp enough to split an infinitive
Sharp enough to cut a rug (To dance: ie;dance about holding the bleeding apendage shouting 'blinkin' flip!' or words to that effect)
Or as Horatio Kane once said to John J Rambo ' THATS Sharp, what do you hunt, Elephants?'