The patagonia sun shade hoody is my favorite for wearing at high elevation or on the water when there is some wind though it can be too hot if their isn't wind.

For warmer conditions there are some great pieces in their summer trail running line (on clearance at the moment) including the air flow and gamut shirts:

http://www.patagonia.com/us/shop/web-specials-mens-trail-run...

Edit: opt for the stuff with mesh zones, the straight cap 1 stuff doesn't breath as well. Their merino 1 t shirts are also nice.

Also check out fly fishing clothing by them and others for sun protective clothing with a less athletic look.

I've been using this one for a few years now and love it: http://www.rei.com/product/862927/rei-sahara-tech-long-sleev...

SPF 50, tons of pockets, quick dry material, vents in the back and armpits for air circulation. It even has little snappy things to hold your sleeves when you roll them up.

The added benefit of a shirt over sunscreen is that the shirt keeps bugs off too.

Check out Solumbra products - http://www.sunprecautions.com/

I have one of their long sleeve "jackets" that you can wear in the water. Their products are not cheap, but they do last a long time, mine is over 10 years old.

I like the Columbia Omni Shade clothing, for example: http://www.columbia.com/Omni-Shade/Technology_Omni-Shade,def...