[SDPhantom]

I wrote my own script to do this a long time ago and decided to dust it off and make some improvements. It should work with Classic Era, Wrath Classic, and Dragon Flight.

local function UnequipAll()
    local invslot,lastslot=EQUIPPED_FIRST or INVSLOT_FIRST_EQUIPPED,EQUIPPED_LAST or INVSLOT_LAST_EQUIPPED;
 
    ClearCursor();
    for bag=NUM_BAG_SLOTS or NUM_TOTAL_EQUIPPED_BAG_SLOTS,0,-1 do
        local free,type=(C_Container or _G).GetContainerNumFreeSlots(bag);
        free=(type==0 and free or 0);
 
        for _=1,free do
            PickupInventoryItem(invslot);
            (bag==0 and PutItemInBackpack or PutItemInBag)((C_Container or _G).ContainerIDToInventoryID(bag));
 
            invslot=invslot+1;
            if invslot>lastslot then return; end
        end
    end
end