My name is Ken. I have a calculator problem.
I use a HP 32S at work, HP 34C at my desk, and HP 15C at my lab bench. I love them all but generally recommend the 15C for those benighted souls who have yet to discover why HP zealots are sold on RPN. Because I've used it longer than the others, the 34C has a special place in my heart, but the "1/x" key (used frequently in RPN operations) is a shift function, which makes it harder to use than it should be. The 15C gets it right in all the important places. The long-discontinued 32S has base conversions, which are great for software work.
Aside from the 15C, the current HP RPN offerings are problematic. The 35S has its charms (fractions, for example), but the display resolution is so coarse I find it hard to read, the format is too big and clumsy, and I still can't forgive HP for making "STO" a shift function. The 50g is a fascinating machine that I would choose for an eternity of solitude on a desert island, but it's a dreadful calculator for almost all practical purposes. (I will also admit to a small collection of "antique" HP calculators, but I don't use them as my daily beaters...)
I have explored HP calculator apps on my iPhone, too. My favorite is "VintageRPN", which includes an emulation of the original 35 and 80, arguably the most usable and inspired HP calculators of all time. And once again, they are highly usable, even on the tiny touch display of the iPhone.