IF I wear underwear (and I'd say I only wear it about 50% of the time or less) I wear Adidas ClimaCool ones. They are like tighty whiteys but have a little bit of "give" to them. I wear them when working out. Just the feel alone of wearing them makes me hard.
These are the exact kind I wear: http://www.sportsauthority.com/prod...fbn=Brand|Adidas&lmdn=Brand&parentPage=family
These are the exact kind I wear: http://www.sportsauthority.com/prod...fbn=Brand|Adidas&lmdn=Brand&parentPage=family