At 4.2 ounces, Saucony’s EXO jacket may not only be the lightest running jacket out there, but is also the lightest fully waterproof, hooded jacket we have ever seen. The jacket comes with fully taped seams and a stretchy film laminate; a deep hood; a slim, runner-friendly fit; and one baby chest pocket. You’d be hard pressed to design a lighter squall protection system for runners who are conscious of every gram.