Our top rated and lightest lightweight shell is the Arc'teryx Alpha FL. This piece weighs a mere 10.7 ounces, has is slightly more breathable material than the Ashdown. The Quasar is our top rated lightweight hardshell for hiking. Other superlight rain jackets will be lighter (by about 2 ounces) but none will be as durably waterproof as the Quasar.
Stepping into the medium duty category, the 14.1 oz Patagonia Super Pluma is out top rated all-purpose hardshell, and the winner of our Editors' Choice Award. Go for the Super Pluma if you want one shell for skiing, hiking, climbing, and everything else.
For the most durable and versatile piece of mountain climbing body armor choose the Arc'teryx Alpha SV. This shell represents the ultimate in simplicity and function, and boasts a slew of well refined climbing specific features. The Alpha SV is ideal for climbing mountains that cross multiple climates: start low by bushwhacking through dense, wet forests and finish up high on technical ice and snow. The Alpha SV is much more durable than the Ashdown. It's also more durable and has more room for layering than any lightweight shell or the Super Pluma.
For those on a budget we recommend the Rab Stretch Neo. Available for around $350 this jacket is nearly half the price of the Arc'teryx Alpha SV, weighs nearly the same amount, and has nearly the same feature set. It's an excellent value.