Day time sunny - Kenneth Cole Reaction progressive tint sunglasses. Darker towards the top, lightens towards the bottom. It's a "medium" towards the top, and a "light" towards the bottom.
Day time overcast, night time - 30 dollar pair of cycling/athletics wraparound amber polarized sunglasses. I prefer to wear these generally. Picked them up at a Dick's Sporting Goods. Was ready to drop 60 or 70 dollars on a "good" Serfas or otherwise pair of glasses, saw these, tried them on, and didn't need to try any others on.

If I'm wearing one, the other is in a side pocket of my pack to swap out on the fly.