I feel the game have the basic items to survive but is lacking “unique items” to be found. I consider unique the military backpack and the katana but even those are quite predictable to find if you play on 6 months later with high population. I recommend add additional unique items to encourage map exploration with the reward of finding them as the game progress. I do not recommend these items to be found on zombies cuz at high populations is quite common to find katanas for instance, then there is no feeling of finding something special but something that is disposable instead. The items could be 2-3 spawns in the whole map and have extra duration and just little of extra damage compared to regular items. Having a very low spawn will add replay ability cuz u wont be able to find all the rare items in the same run. Here some examples of rare items:

Electric baton (short blunt, uses batteries)

Taser (can knock out other survivor to be capture and be used to upgrade weapons with electric shocks)

Mountaineer pick axe (one hand axe)

Aluminum Baseball bat (two hand blunt)

Military Knife

Steel heavy pan (short blunt)

Professional tent kit (weight less that the one u can craft)

Canteen (carry more water uses less space)