The Western Flyer from Tom Bihn is a small duffel/backpack conversion travel bag designed for quick trips or minimal travelers.
Other Bags to Check Out:
The Wilderness Rucksack from Tanner Goods is a gorgeous, artisan, hand-shucked heirloom bag that your grandpa would be proud of (whichever one of your grandpas was more badass).
Ok, these bags from Nomatic are chock full of pockets. There are 2 different bags: the Travel Pack expands up to about 30L, perfect for short trips and minimal travel. The Backpack is 20-24L daily carry. Both are very sleek and, like I said, so many pocketzzz!
The Dayfarer backpack is one designer's take on the perfect bag for work and gym.
The Headway MLC (Maximum Legal Carry-on) from Patagonia is a very functional gear bag that works better as a duffel due to it's uncomfortable (but hideable!) backpack straps.
The Monolith Weekender from Heimplanet is one of my favorites because it is very durable and simple. Carries all your shit, and comfortably!