The only two things I can think of, which aren't really that special are a modified flat blade screwdriver with a slot cut in the end to help undo/do up the slotted nut on the hinge bolt on the later BSA Mercury and Challengers, I also got my friend who has a lathe to make me up a small boss that slides over the spindle on my bench grinder so I can use an angle grinder cutting disk to cut main springs as I always found it a pain trying to cut through springs with a hacksaw.
Pete