Spigen Tough Armor
I got my Spigen Tough Armor for the s5 on Tuesday, and it's by far my favorite case I've owned for any of my devices. Definitely prefer this to Lifeproof and Otterbox overall. You can find it on Amazon here
It's slim, the buttons click easily, and the heart rate monitor and fingerprint reader work like a charm. Only issue is until you get used to it it is a bit difficult to get the charging cover open, but after a day or two of doing it it's pretty easy.
Says it's compatible with Spigen's glass screen protectors as well, I'll be getting one soon.