Probably the most useful piton for climbers is the medium bird beak, of which the medium Moses Tomahawk is the best model at the moment. The reason for this is that a beak will go where no passive gear will, i.e. smaller than a microwire or micro cam. These can be hand place and hook into placements where a nut would go, but its cable won’t, or hammered into all sorts of places, both singly, or stacked with other beaks, or nuts (this way you get both a hooking piton and a compressed piton). Of course, this image is not a beak, but a universal piton, in this case, a small @grivel Top 75 Universal, a piton I’d say is the next most useful. The reason for this is that a piton like the Top 75 is very small, light (113 g), and tends to go in many of the places you need a piton to go, and can be invaluable for winter climbing, as well as alpine climbing and adventurous rock (especially limestone). They rack away really well and provide very solid placements. The reason why size and weight is important is that you really don’t want to be placing pitons if you can find something else - for various reasons - but when you need to, you’ll really need to. Image from upcoming book ‘Down’.