Best for carrying large and small loads: Eagle Creek Morphus 22

Head out with one bag; return with two. This lightweight carry-on morphs from 48 liters to 95. How? Its front gear bag zips out to be used as a backpack, so you can overstuff when the occasion calls for it, or go simple for more rugged trips. A bathtub construction keeps your stuff dry. [$395; eaglecreek.com]