I use Skullcandy Titans. They are really good and have a cord that is slightly longer than normal buds, so you don't get the pull from your pocket or neck when doing a bunch of full body stuff.
I also have a pair of Forte Audio Impacts. They are the best buds I have ever had. I care less about the titans, though, so I use them more often in the gym, and my Impacts more often for work.