I think my 'best' in terms of favorites, would be:
Discord
About 90% of my internet social time comes from Discord as I'm a part of a lot of gaming, K-pop, and other hobby servers, as well as the Wonderland server to keep track of what's going on the staff side of things.
Add to this, the desktop client that syncs up with the mobile version and vice-versa, Discord is a well-unified app to use both at home and on the go.
Twitter
I love Twitter to keep up with K-pop groups, friends, companies, as well as having some general fun with my Twitter social circle.
Spotify
I absolutely need my phone for music, and Spotify is one of my most crucial apps to have.