Liquid Paper

Or more correctly in this case, "correcting fluid" (Liquid Paper is a specific brand name, invented by Bette Nesmith Graham (mother of Monkees member Michael Nesmith) in 1951).  I used to use liquid paper in high school but it always dried up before the end of the bottle was reached (oh the joy of a fresh new bottle of liquid paper!).  

So I was pretty excited when Pentel came out with a better applicator, and used those forevermore (until I left uni anyway heh).

And I was even more excited the other day when I found a bottle (still liquid!) in one of Stu's pencil cases. :)

Pentel Correction Pen