Currently using a Kyocera DuraXE. It's great and still has a very inconvenient to use subset of the functionality you might miss from a smart phone. I bought it because I needed hotspot tethering for work. However, I've recently read that the Light Phone II has that feature and is even dumber of a phone, so might switch over to that.

Previously I was getting by fine with a pre-paid LG flip phone and buying around $100/yr of minutes/service from TracFone.