Heres the equip script:
local equipped = script.Parent.Parent.Parent.Handler.Equipped
local selected = script.Parent.Parent.Parent.Handler.Selected
local location = script.Parent.Parent.Parent.Handler.Location
local player = game.Players.LocalPlayer
local character = player.Character
script.Parent.MouseButton1Click:connect(function()
if equipped.Value == nil or equipped.Value ~= selected.Value then
character.Humanoid:UnequipTools()
if location.Value == player.Backpack then
character.Humanoid:EquipTool(selected.Value)
equipped.Value = selected.Value
script.Parent.Text = "Unequip"
end
else
character.Humanoid:UnequipTools()
equipped.Value = nil
script.Parent.Text = "Equip"
end
end)

2 comments
You can't equip and change weapons on death, logically it wouldn't make sense.
lets put it this way. I meant like when you equip something in your inventory, how can you make it to where you can only have 1 weapon in your backpack at a time