That said, when I don't have a hand-held calculator handy, I usually just fire up bc or R when I need to do some quick calculations.
Those who prefer RPN should check out dc! It's my preferred calculator for simple calculations.
The -l flag changes that behavior to instead use 20 decimal points.
In the final year of high school I was taking a class that did not require a graphing calculator, so I bought a TI 36X Pro, an advanced scientific calculator. It has excellent 'UI', tons of functionality, and the buttons feel great to type on (though after a long time they will still start to get mushy). I actually used to carry both of my calculators with me, the CAS for when I needed it and the 36X for normal usage since it felt better to use.
It's not a school monopolozer like the 84/89 so it's priced well, at <$20. I bought another one in college after I lost the first one. I'm doing CS so I don't need it often, but I find it to be worth keeping around.
(I still consider my HP 48SX My Precious, though. Yay RPN and all that.)
Turns out it sucks, and I wound up just buying one of the $5 solar basic calculators and was way happier. I can't wait for this monopoly to get blown up.