3GS
4S
5S
6S+
XSMax
??13PMax?? Can't wait for that massive screen, smaller notch, promotion and MaskID (maybe...)!
But ranked in order of my favorites...
3GS - really dug the fun two tone design although didn't sit on a table all that well. It was tiny, but that's what phones were back then.
6S+ - My wife is still rocking this phone. It's been an absolute workhorse and apart from the battery hasn't needn't anything replacing. It is having battery issues again though just recently.
5S - The best design of the lot IMO and pretty sure it introed TouchID. Camera was very, very ordinary but the Space Gray looked fantastic on it.
XSM - Great size, but it has the intel modem. It's been perfect to use, but I dislike the notch.
4S - I loved Siri when I got it and it felt like the future, but everything else about the phone was just solid. I never liked the 4/4S design which I know many people do.