I use a passcode.
This way I don't accidentally unlock my phone in my pocket. Sometimes you can accidentally press the Home Button against your leg in your pocket.
Other phones have a recessed home button, so it's harder to do that.
The S5's home button protrudes, so its easier to accidentally "but-dial", so to speak.\
I would take my phone out of my pocket some days and see like 12 apps opened, the phone dialing someone, text messages like "dkfjnq4fn4ofun4aiufniunvi" sent to random people. It's was quite interesting lol. One time my mom started talking to me from my pocket. I am not even joking. Right after I took out the trash, I hear, "Oh Hi. What's up? Did you call me? " from my pocket. Completely freaked me out.
So I added a 4-number pin lock and now I'm cool.
If I somehow manage to dial that exact number inside my pocket and unlock the phone like that, I'm selling my S5. lol