For me, the HP17BII+ is probably the best hidden secret of calculator world today. I don't know why it isn't sold much, much more. It has the feature set of the original HP17BII (minus a couple of only-programmable functions for the solver that I have never used), plus a new menu for currency translation (very useful when you're analyzing a foreign company financial statements), and a much, much (did I say much) better screen. It also has much more memory that you can use to store many solver formulas.
And this is the beauty of this calculator: the solver. While the mighty HP42s had vectors and matrixes, it lacked a simple, programmable solver that solves your day-to-day problems in a much more flexible way than the typical program. And it can do loops and ifs, if you want to spend time; but that's not its purpose.
It also has a lot of menus made for the financial user - and a math menu that frankly it would be enough for the scientist - if only it had trigonometrics too.
Let's see the menus for a while:
FIN: finance. Time Value of Money, interest compounding, cashflow analysis, bond calculations and depreciation
BUS: useful % calculations: change, total, markup on prices and margin on sales. Very easy to use and fast!
SUM: statistical calculations on one or two variables, keeping all the data sets (different from the 12c and other units that have statistics). You can go to any sample and change it. Eventually you could plot it if you had the printer.
TIME: this calculator keeps a clock and can do all kind of time calculations, and keep appointments and alarms. Like the HP41C Time Module - but much better and simple to operate.
SOLVE: here is where all your formulae are. Extremely powerful - if you know your business and set to make it easy. (Calculate prices that go according to a formula involving market commodity prices, currencies, etc. is a very simple thing with the solver)
CURRX: currency calculations. You can have many pairs of currencies defined. Once updated the exchange rate, you can easily make all calculations.
On top of all that, it looks the part too: the metal surface is quite resistant, and the plastic back extremely so. It could print, too - only if you found an infrared printer, which are out-of-market nowadays.