My good buddy is an old HP-41C calculator, loaded with a number of specialty programs and conversion factors. God knows what I'm going to do when it finally breaks down. Now and then I have to whap it on the palm of my hand to get it started...

I kept screwing up decimal points with a slide rule. When my high school chemistry teacher brought in an early electronic calculator (about the size of a typewriter with a little green screen), I was in heaven. A few years later, I managed to convince one of the guys I worked for to spring for an HP-35 (little red LEDs!). Been an HP reverse-polish-notation man ever since.

My first real calculator

My current good buddy (you need to imagine it with a bunch of little labels stuck next to the keys to identify programs and conversion functions)