It is a largely ignored truth that sibilants – those wonderful hissing sounds – are the noisiest, most attention-grabbing elements in speech.
To that end I am going to have visiting cards printed up as follows:
whithper during a conthert
They would have been useful this evening.
[Many thanks to C.S. Lewis who brought the highly useful tip about lisping to my childish attention in, I believe, The Last Battle.]