"Butcher’s knife
Before developing an official-issue fighting knife, the French Army purchased all sorts of knives from private firms, such as this butcher’s knife.
200,000 of them were ordered in September 1915. Many were used by teams of ‘trench cleaners’, who went in after an attack to make sure no German remained alive.
One trench cleaner, Louis Corti, wrote, ‘We were armed with a dagger, a revolver or rifle and a bag of grenades...the watchword was “No Mercy”."
The British and Germans used clubs:
"Trench clubs
The club was used on trench raids and patrols to kill silently.
The clubs above are German, those below and right British. They were made in army workshops or improvised by the soldiers who carried them."
http://www.iwm.org.uk/sites/default/files/public-document/Fi...