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.