Seeing as I didn't read this last time (or if I did, I forgot)
Plain biscuit - butter crunch, or malted milk, depending
Chocolate biscuit - plain choc digestive
Wrapped chocolate biscuit - don't really buy them, too many layers between me and the chocolate
Savoury biscuit - used to be high bake water biscuit. Now those ones with seeds on, with oatcakes a close 2nd