PCalc 1.7 (for iPhone)
If you turn on the HP48 Style RPN setting, PCalc 1.7 does the right thing: it enters the number in the x-register and waits for you to type another number before pushing the entered value into the y-register.
I also like the orientation lock, the 4-line display, and the faster launching. PCalc was always good, but now it’s really fantastic.
