Hmmm...
D&D has probably given me hundreds of words, but I've been gaming for so long that its hard to pinpoint which came directly from the game. Recently, I was looking through a book someone left laying around called Vocab Rock. Vocab Rock is meant to serve as a study guide for the SAT and ACT tests. Glancing though it, I noticed that a number of the study words crop up all the time in gaming. For example:
Illusion, ignited, razed, incantation, resplendent, craven, comely, annihilate, labrynthine, decipher, esoteric, neophyte, infinite, loom, cosmos, dispel, faction, phoenix, toxin, traverse, colossal, panache, and thaumaturgicaly. That's just in the first half of the book.
A few that I can recall specifically looking up because I saw them in a gaming book:
Sepia (Player's Handbook)
Fane (various adventures)
Abjure (Player's Handbook)