At the marathon I wore this long-sleeved Mizuno Comp Diamond Long Shirt. I felt very comfortable in my new running shirt throughout the race. It absorbs most moisture well. I've worn the Mizuno brand well.
Pros
The shirt fits very well and is very light.
Cons
Limited Color Options: The Mizuno Comp Diamond Long Sleeve T-Shirt is only available in one cardinal color, which may not be to everyone's liking.