This is for one part.
local mouse = game:GetService("Players").LocalPlayer:GetMouse()
local part = workspace.Part --Your part here
while task.wait() do
part.CFrame = CFrame.lookAt(part.Position,mouse.Hit)
end
This is for a model.
local mouse = game:GetService("Players").LocalPlayer:GetMouse()
--local part = workspace.Part --Your part here
local model = workspace.Model
while task.wait() do
model:PivotTo(CFrame.lookAt(model.PrimaryPart.Position,mouse.Hit.Position))
end