Great topic idea @AnkerOfficial! It's always fun to read about the apps people use most in this Age of the Apps that we live in. I linked all the apps I mentioned below to the US iOS app store. I use an iPhone, so it was just easier for me to use that format. No prejudice against Android users.
There are few apps that I use on a regular basis. The most used is GIPHY to send gifs via text. I feel like if you don't already have this one installed on your smart phone, you're missing out on the most fun way to express exactly how you're currently feeling and you're probably not getting the precise tone of your text across to the receiver of your text.
Next is Runtastic. This is a great app to track your exercise and even communicate with other users from around the world. There are several stand alone apps for heart rate, eating, and even push-ups and sit-ups.
Google Photos is another great app for those that have a lot of photos and not a ton of phone storage space. It allows you to safely back up all your photos for free with unlimited storage and access across all devices and even the web. I do this about 3 times a month before backing up a copy to my hard drive at home and then deleting all the photos and videos from my phone.
The last of my go-to apps is the Amazon Alexa app. I use this app ALL THE TIME primarily for my grocery list. It's become easy and affordable to acquire an Alexa device these days, so adding something to your shopping list is as simple as saying, "Alexa, add milk." Now when I go to the grocery store, I have everything I need to buy right in front of me since I never leave home without my phone.
I haven't seen anyone mention these apps yet, so if you haven't tried one of these apps, download it and give it whirl. You may enjoy it as much as I have! Happy "apping"!