The one phone that has been a constant in my life for quite a few years now is the Motorola V551.
Yes, it is a flip phone. Don't judge me! I loved this thing from the day I bought it and I still love it. While I couldn't use it as a daily gadget these days, I still bring it out from time to time if I know there is a chance I might be taking an unintentional fall or swim. Fishing and camping trips are when it sees the most use these days. To me though, it is still the perfect cell phone. Obviously, I don't even put most of the newer devices into the "cell phone" category. My iPhone is not a cell phone, its a damn computer.
But the Motorola V551 is just a phone. And it does its job well. The best sound quality of any phone I've ever owned. It had insane battery life and was just tough. It has been dropped and kicked and thrown and otherwise just generally abused and it has never once had a single operational issue. Sure, it isn't the most beautiful thing in the world, but I still love it.