With over a dozen of car mounts I reviewed recently, I have to admit Arkon Mobile Grip 2 (http://www.arkon.com/mobile-grip/) is still my top choice, currently for $19.95 including shipping on Amazon (http://www.amazon.com/Arkon-Windshie...dp/B00I58VAZS/). Though I have reviewed it already with my Note 2 (http://forum.xda-developers.com/show....php?t=2648852), some ask me how does it look with S5. Now after getting Galaxy S5, I've been using MG2 in my wife's Highlander and still find it to be the best car mount for the phone.
It's sticky suction base mount adhesive is as strong as a cement attached to any glass or textured dashboard; works even on a slightly curved surface. The removal is clean and doesn't leave any residue, plus it's re-usable - just rinse under a water if it starts to loose it's sticky grip. The mount arm accommodates different angles with an easy adjustment, and universal ball joint allows full 360 degree rotation. The spring loaded grip is very secure and easy to operate with one hand, and it's minimalistic design keeps the back of S5 open to use even as dashcam. Obviously, there is full access to all the ports for charging, headphone/audio cable, and power/volume buttons. As a bonus, MG2 also has a screw mount for universal camera tripod attachment (love it!). Also important to note that it comes with 2-year warranty, and from my experience Arkon guys stand behind their product to take care of you even after warranty expires.
Since I know pictures worth a thousand words, here you go for your enjoyment (with more pictures you can find in my Note 2/MG2 review above).