I understand everyone's HP-10 series nostalgia, but to replace the TI-83 on that list would have to be the HP-48 series. Full graphing and programming capabilities, released 3 years before the TI-83, and of course using the all-but-forgotten RPN.
I always wanted an HP-48 in place of my TI-83.... so much so that I ran an HP-48 emulator under Linux. If I was working from a campus lab, I would VNC into my own machine just to run the emulator.
There's a great HP-48 emulator for Android in the play store (and some great TI-8x emulators too).
I love the RPN on the HP-48, but the HP-16C was built for programmers so it will always rate higher for me.
I have an HP-12C financial calculator, that I use regularly, and it's still on the original battery.