I have Endomondo Pro, Runtastic Pro, Runtastic Pedometer Pro, and I also have Fitbit for my Fitbit Flex.
Sadly my Flex cant sync with my HTC One nativly just yet so I have to sync it with my mac. However the app still works for logging other exercises and food / calories and water.
Yahoo Sports is great. It's fast and doesn't use up RAM once you are done using the app, I remember Scorecenter used to stay as an active process even when you exited it.