For game design, any or all of these will easily be in most top lists:

- Tracy Fullerton's Game Design Workshop

- Jesse Schell's Art of Game Design A Book of Lenses

- Steve Swink's Game Feel

- Scott Rogers' Level Up

- Skaff & others' Characteristics of Games

- Raph Koster's A Theory of Fun

- Joris Dormans & Ernest Adams' Game Mechanics: Advanced Game Design

This one was just published but I'll happily bet on it:

- Richard LeMarchand's A Playful Production Process