I usually buy ridiculously gaudy sunglasses with rhinestones in them. However, when getting ready for the 2008 trip around the world I knew I'd need something a little more practical.
After extensive research, I picked the Maui Jim Titanium Sports.
I was initially heavily biased against these glasses because I think the name "Maui Jim" sounds like something only tourists with Polaroid cameras would wear.
However, these are serious performing glasses. The lenses are very high quality and are polarized. This is no gimmick - they completely eliminate dash glare on even the most freshly Armorall-ed cars. Roads look black even during blinding sunlight. It's pretty amazing.
They weigh only an ounce or two - so little that I always forget that I have them in my pocket. Then I take a nap and crush them. So far they have yet to get bent out of shape.
Best of all they have no springs so you don't have to worry about little adjustments while you're traveling. The titanium sides just bend to the appropriate size.
They look cool, perform well, and weigh as much as a few candy beans. I love them.