I just went around writing my second book when I thought of this question to say on the forums:
What are your favorite video game quotes? If I had to pick from my list of favorite quotes it would be: SL: "Warning, this tutorial shows the advanced menus..." - Torley Linden
WoW: "Persistance or stupidity? This means not. Let there be a lesson taught to you, mortal!" - Arthas, the Lich King (Howling Fjord)
TF2: "I never was really on your side." - Spy
War3: "I'm your shooter." - Riflemen unit
Brawl: (seriously.) - "Falcon PAWNCH!!" - Captain Falcon
But overall the best quote has to be this:
"Do a Barrel Roll! Press Z or R twice." - Peppy Hare (Star Fox)
Surprised? Post your favorite quotes here if you want to.