Frixion erasable pens are hugely popular in Japan, but relatively unknown in the States. I didn’t even hear about them myself until 2012, though the product has existed for 5+ years.
Frixion pens are not the smearing horror pens that you may have used in school — the ink is not rubbed away — it actually becomes invisible when heated with an erasing motion of the rubber tailcap. No eraser dust is generated.
This pen allows me to take correctable notes at work at the speed and detail I desire, yet have the text be dark enough that the resulting documents can be read when scanned.
As electronic documents become more popular, I think Frixion pens will have a bigger role in replacing mechanical pencils, whose gray output is not always clear when scanned.
The pens come in gel, marker, and highlighter types with various colors. They are easy to come by at your local office and grocery stores, and are as cheap as $2 a pen.
Of course, I wanted something with a finer tip, and more business-appropriate, so I sprung for a 0.4mm, metal-frame LF-2SP4-B business-style Frixion pen.
Note: Because the ink disappears under heat, do not leave your notes in a car on a hot, summer day, as they will disappear. They are recoverable by putting the document in the freezer, however. That brings up a concern about whether or not text erased by the tailcap can be recovered in the freezer. From my experience, when the tailcap is used to erase text, it’s mostly unrecoverable by the freezer method.