Sperry Topsiders
The Timberland boat shoe slip-ons are very comfortable and I've had no problem walking from one side of Boston to the other. They've got a little bit of an old man feel to them, but there are a few swankier pairs here and there:
http://www.timberland.com/family/index.jsp?categoryId=1770276&cp=1779791.1761081
Sanuk Sidewalk Surfers. Where them as a full-back shoe or a no-back shoe. Socks or no socks, and very comfortable. Your feet will not sweat due to the breathable canvas upper.
Easy...Patagonia Maui Air. I've had mine for a few months and I'm thinking of getting a backup pair. They're super light and super comfortable. A great summer shoe.
Maui Air: http://tr.im/kNyu
If you're in colder climes, check out Patagonia's Maui Moc; similar to the Maui Air, but with a cushy fleece lining. Never tried them, but if they're anything like the Air, you'll love them.
Maui Moc: http://tr.im/kNyF
I can recommend Blundstones as an excellent walking around boot/shoe. I've done a lot of travelling wearing these and have had no problems and walked miles.
New balance. They have classically styled shoes made for walking, most comfortable shoes out there.
Please provide links to products you recommend or your answer will not be accepted.
Use this code to make a link. "Product Name":http://www.example.com → Product Name
Should I buy Sperry boat shoes in a smaller size than normal?
Can I wear my suede desert boots with a suit?
Where can I get a manly-looking reusable grocery bag?
Where can I browse hairstyles for men?
What is the best dress sock for sweaty feet?
Should I buy leather dress shoes that can be repaired instead of replaced?
For a casual look, I am a fan of old school vans