We tested half a dozen jackets weighing less than 10 ounces, and the Nano rose to the top. "Most ultralight shells can handle some drizzle," said a North Carolina tester, "but this one rocked three solid days of sideways April rain in the Shining Rock Wilderness."
After weatherproofing, breathability is often the main concern in this category, but the Nano uses Gore-Tex Paclite, which testers said caused little steaminess. Plus, you can enhance airflow by unzipping the vented pockets (no pit zips). The tiny zippers and hardware look handle-with-care dainty, but proved plenty tough. A Nano feature we wish every shell had: a wire stiffener in the hood's brim that lets you shape the visor for a custom fit. $250; 6 oz.; men's S-XL; marmot.com.