This question began due to a certain fictional monster. Where it was stated to be able to secrete explosive goo activated by its saliva, which would coat its boulder-like arms and explode when smashed against the ground (or human whichever works best).This creature has nothing to do with the question, it is however the origin.
Which led me to contact explosives and Nitroglycerin. Okay, so Nitroglycerin isn't exactly the most safe substance to transport even by modern standards but I insist that it should be Nitroglycerin (Think of the possibilities, nitroglycerin-propelled spikes and bombs).
However, what would allow a creature to produce Nitroglycerin and then store it for future use?
The biggest problem might be storing such a volatile substance, as funny as it might be to have creatures that explode when they walk it doesn't make for a feasible real creature.
I only need a biological way for a creature to store this in its body and to produce Nitroglycerin, there is no need to work out other things like how it might have evolve and additional organs that would allow its use in one form or another. It is a nice bonus of course.