1. My Fitness Pal
This is a food and exercise diary. It is one of the best on the market in my opinion. There are a lot of users adding new foods so you rarely have to add anything yourself. The barcode feature is priceless and saves so much time. I use this app multiple times a day absolutely every day and I love it. The app sync's with my FitBit and also allows me to print off (in PDF) and email it to my trainer.
2. Nike Training Club
Yes, this is a GPS tracking app. This one is so different to any of the others I have seen though. It allows you to track your different workouts differently - I always had trouble with other apps because I couldn't track my walks differently to my runs so average speeds and what not would be affected. Srava also allows you to import from your GPS device, so it is an app but you can also jump on the computer and import from your Garmin. Then you can also put in your cycling, hikes, or any other workout type you want to track. Then you can connect with your friends and see what they have been up to.
4. Gymboss Timer
Quick tabata workout at the gym? no one has time to watch their phone timer constantly when they are trying to go all out, so that is where this app is brilliant. It is simple, easy to use, has lots of options and I am told operates just like the Gymboss timer except that it is free and it is on your phone so you always have it with you.
This may seem like an odd addition here but believe me, I have a bunch of so called Fitspo (fit inspiration) accounts, that make me feel like working out when I am tired and have zero energy. A quick flick through a bunch of shots of 10km runs, videos of pull ups and 6-pack abs make me get off my butt and do some squats.
What are your must have fitness apps?