Joby GripTight Pro 2 Mount

I own THREE of these, and they're on basically every tripod I use with my phone. I honestly love them.
My favorite thing about this mount is that it actually locks my phone securely into place. Once I tighten it down, I'm not constantly worried about my phone slipping out or falling like I am with some of the cheaper spring-loaded phone mounts I've used.
 
It’s also ridiculously easy to switch between horizontal and vertical filming. I shoot in both orientations constantly, and being able to quickly flip my phone, lock it into position, and keep filming makes the whole process feel so much faster and more seamless.
 
I originally bought one and ended up buying more because I wanted one permanently attached to each of my phone tripods instead of constantly swapping the same mount back and forth.
 
If you film a lot of content with your phone, this is one of those little pieces of gear that makes a surprisingly big difference. It's secure, quick to adjust, and easy to use—and after buying three of them, it's pretty safe to say this is my go-to phone mount.