I have been planning on paying for AppleCare and not using a case for my main phone or an incredibly thin discrete/minimal case. Modern phones look so sleek without cases.
Mine slipped not once, but twice in a cab... In the span of a week...
As much as I loved how it looks and works without a case, they are a slippery nightmare
I think the last phone that felt good to use without a case was the Nexus 5.