Has to be Crunch Creams by a mile! Closely followed by Bourbons.
However on a side note, the army issued biscuits come in two types. Biscuits, Fruit and Biscuits, Brown. Seriously!
Biscuits,Fruit are loosely based on Garibaldi. And also in the ration pack come a tube of fruit spread( or jam as the civilised world knows it!) which can be spread over the biscuit as a snack, although it can also be used for dunking in a strong hot brew. Some people also spread paste or cheese on it, it doesn't matter as the taste is the same!
Biscuits,Brown however are a totally different kettle of fish, these can be used as anything at all to supplement your scoff. They can be broken down to put in your soup,(croutons!) to stodgy up a stew, (stock)or as an alternative to the above, with the spreads, however they are much harder to chew and therefore this is pretty much avoided unless necessary. However, on the Peter Kay point of the hardest biscuit in the world to dunk, nothing could ever beat the Biscuit, Brown. Seriously, theres nothing like it!