Don Knuth

From Pre-Fascicle 1a: Bitwise Tricks and Techniques (version of 03 Jan 2007) of Volume IV of Don Knuth's Art of Computer Programming:

A trick is a clever idea that can be used once, while a technique is a trick that can be used at least twice.

This raises the question—what's a trick that has been used at least three times?

Two possible answers:

a) Homework
b) The "Research Publications" portion of a curriculum vitae