If you are interested in this subject, you should definitely go check out The Great War:
Today we are discussing some of the hand-to-hand melee arms of the First World War – specifically trench knives, trench clubs, and field spades. The up-close confined nature of trench warfare in WWI was not anticipated by its planners, and the infantry rifle/bayonet combination which had been developed for use on the open field was of little use in the trenches.
In response, troops adapted a wide variety of improvised weapons that were more suitable. Some became issued formal items, and some remained ersatz and handmade throughout the war.
Perhaps the most effective was the field spade, which was often sharpened around its while perimeter and could be used as a very utilitarian hand weapon in a variety of situations.