Daffy/ Daff is quite often used in Wales. I'm not sure how keen I would be on them being used by someone without a Welsh accent though. Possibly 'D': My Dad calls his brother
Oliver 'O', and it works. I do like
David on its own though.
I like the name
Amadeus, but it does seem to cry out for a nickname, if only to be used by friends. Somehow none I can think of seem to do the full name justice though.
My thoughts: Am,
Ami, Amus,
Adi, Mad (pronounced with a slightly shorter a than the adjective). My favourite attempts are Amo and Dei.