Script of destruction? Is this possible to do?

You're going to want to learn about dictionary style arrays to prevent certain items from being deleted (think how people use admin scripts to stop you from entering a door), pcall() to prevent your script from stopping due to errors, ChildAdded for when objects are added during your game, and for loops to dump everything in the Workspace when your script loads.

local whitelist = {camera = true, terrain = true} -- names and classnames you don't want affected
local ws = game:GetService('Workspace')

local function remove_item(obj)
    -- if obj is not in our whitelist, then we proceed.
    if not whitelist[obj.ClassName:lower()] and not whitelist[obj.Name:lower()]  then
        -- Some items can't be removed, so use caution with a pcall() 
        if pcall(function()
            game.Debris:AddItem(obj, 0)
        end)then 
            print(obj.Name.. " was removed.")
        else
            print(obj.Name.. " couldn't be removed.")
        end
    else
        print(obj.Name.. " was on the whitelist")
    end
end

-- Anytime something is added to Workspace, it will get sent to the remove_item function.
workspace.ChildAdded:Connect(function(obj)
    remove_item(obj)
end)

-- Makes sure everything is removed from Workspace on load.
for i,v in pairs(ws:GetChildren()) do 
    remove_item(v)
end

How about this:

for i,v in pairs(workspace:GetChildren()) do
    if not v:IsA("Terrain") and not v:IsA("Camera") then
        v:Destroy()
    end
end