Endomondo

I was surprised to not see Endomondo here, so I had to add it! I've tried out all the major fitness tracker apps, several of them in their premium forms, but Endomondo comes out on top all the time.

For me, the main thing it comes down to is knowing my heartrate during a run, either through audio prompts or by glancing at my Android wear. I use a Polar chest heart rate monitor, and while other apps track my heart rate, it's harder to know it during the run.

Other than that, I love its large set of features. It's the among the more customizable fitness apps, while still maintaining a sleek interface.