Many years ago I was considering writing a book about dunking. Who dunks what, where you can/can't dunk. (Was planning to go for tea at Claridges, Savoy, Dorchester etc and do a bit of blatant dunking and check the results on a sort of raised eyebrowometer)
As a child my favourite dunk was Maryland cookies dunked in milk. When thinking about the book, I found that all butter danish biscuits were very good dunked in medium sherry 
I'm surprised that no-one had mentioned the ultimate dangerous dunk...........Nice biscuits! Definitely not one for beginners, very much a precision dunk, imo.