In the trenches you will need an entrenchment tool. It will be useful to dig more trenches in the night or make a foxhole to shoot at the Enemy. It can also be used to add onto existing trenches.
Standard Issue Rifle
You will also need your countries standard issue rifle. You can use it to defend your trench. The Standard issue rifle for your country could be the SMLE MK3 for Great Britain, the Lebel Model 1886 for France, M1903 Springfield for USA, Gewehr 98 for Germany, or the Mannlicher Gewehr 88 for Austria-Hungary ("Infantry Weapons").
In the trenches, to protect you head from shrapnel, you need a helmet. You will also need it when you are firing at the other trenches because your head will be sticking out. Also, if something falls on your head, you may not get hurt as bad.
You will need a bayonet in case the enemy storms your trench. It can also be used to cut things like meat and you can toast bread. You can also use it when you are going "over the top" when in close quarters combat with the enemy.
Bayonet. War Relics, www.warrelics.eu/forum/ww1-allies-great-britain-france-usa-etc-1914-1918/ww1-bayonet-274439/. Accessed 27 Mar. 2017.
British Helmet in WW1. Think Link, www.thinglink.com/scene/611198005810298881. Accessed 27 Mar. 2017.
Horse and Man with Gas Mask. David Doughty - Australian Stories - Tribute to ANZACs, www.ddoughty.com/blog/animals-who-served-in-war-ww1-ww2. Accessed 24 Mar. 2017.
“Infantry Weapons of the First World War.” Wikipedia, en.wikipedia.org/wiki/List_of_infantry_weapons_of_World_War_I. Accessed 24 Mar. 2017.
Short Magazine Lee Enfield MK3. World War Relics, worldwarrelics.blogspot.com/. Accessed 24 Mar. 2017.
Soldiers Sitting in a Trench. ARCHIVED, www.collectionscanada.gc.ca/first-world-war/interviews/025015-1500-e.html. Accessed 24 Mar. 2017.
WW1 British Entrenchment Tool. Soldiers of Fortune, www.sofmilitary.co.uk/1908-entrenching-tool-head-stamped-1914-product,15462. Accessed 24 Mar. 2017.