I'm unreasonably excited about my new RPN calculator, a SwissMicros R47. In high school (1995) I got an HP 48G (still works) and was initially confused... RPN is a stack machine, to calculate 1 plus 1, you enter 1 <ENTER> 1 <ENTER> <PLUS>.
To the left is my dad's HP 32S II, which unfortunately died.