Any number of lightweight wicking shirts will do, so I'll make your life more difficult and add another option to the pot.
I was recently given the Mountain Hardwear Way2Cool tshirt from a friend and ran a really long run in this shirt this past Saturday with a nice mix of heat and cool weather. Perfect conditions for testing a lightweight active shirt. I was very impressed with the shirt and how it worked during our outing. The shirt uses MHW's new fabric called the "CoolQ Zero". I don't know what all went into the design of the shirt, but I do know that it wicks moisture admirably and the fit is very much athletic without being too "techy". The colors come in obnoxious orange, belligerent blue, or wanker white. I would say it's most comparable to Patagonia's Capilene 1, but this shirt feels cooler to the touch and doesn't get as warm in the sun as Capilene 1 has for me in the past.