Tools of the trade: The stationery you never knew you needed until you tried it

I enjoyed reading the comments to this Lifehacker post about the things people never knew they needed until trying them — from Roombas to wireless chargers.

Naturally, my next thought was what products fall into this category in the stationery world. Fountain pens do for me, since I didn’t grow up with them and was ignorant of their charms until I bought one. So, too, do Rhodia Dot Pads, which I would never have guessed I’d like as much as I do before I used one.

Readers, how about it? Is there a particular kind of pen, ink, or notebook, an eraser, a pencil sharpener, and/or a different kind of writing instrument that you would never have guessed would become an indispensable part of your arsenal until you took it for a test drive?