I'm gonna throw up a vote for the Old Navy tees.
With warmer temps around the corner, I was in dire need of some basic tees that weren't undershirts. Options around town are pretty limited, so it was either Gap, Old Navy, or one of the A&F type places.
The Gap ones fit very well, but don't seem to warrant the $14 tag (that's if buying two) considering the material. Soft, but flimsy. Fine now, but I could see the neck getting ragged after only a few wears.
The Old Navy ones have a similar cut and felt more substantial. At $7 a pop, they were a no-brainer.