Patagonia Silkweight T-Shirts are really nice year around. I always buy 'tall' T-Shirts so they will stay tucked.
+3 for Hanes.+2 Hanes
+2. The shirts are relatively cheap, very good and last forever!+1 Kirkland from Costco
This is going to seem ridiculous based on price, but if money were no object this is the best T-Shirt I have ever owned:
http://ribbedtee.com/store/product/micromodal-white-crew-neck-undershirt/
Crazy soft, wears well, great fit. I have two of them I bought when they were on sale. (I have plenty of Hanes too!)