[RadioAstronomer]

Nothing beats The Addiator.

A slide rule certainly does not. (You cannot add using a "slip stick") That was one of the few chuckles I got during the movie "Apollo 13." They were adding numbers using their slide rules. :)

[PatrickHenry]

You cannot add using a "slip stick"

At least one manufacturer of slide rules, Faber Castell (German, I think) attached Addiators to the back of several slide rule models. I own one of those. Big-time retro.

[AndrewC]

(You cannot add using a "slip stick")

Yes, you can. Use the C, D, and L scales.(I have a Post)