Affordable and lightweight
The Mammut Smart belay device is a unique assisted-brake device that has a lower weight and price point than the ever-popular Petzl GriGri. While this device may not be intuitive at first, it is pretty easy to lead belay smoothly once you've practiced a bit and is great for TR belaying. Lowering is pretty easy, but perhaps not as smooth as other devices. I would recommend this device for casual cragging. Overall, this is a great device for a belayer on a budget, but lacks the finer points of a GriGri.