So many, but I'll stick to the three: quaff, doff/don, and the use of former and latter. I'd heard of the latter but not the former.
D&D is singlehandedly responsible for my dominance in scrabble, boggle and the like. Hey! There's another one: "the like".
D&D also taught me rapid simple calculations, percentages, statistics, simple cryptography, creative writing, public speaking, leadership, dealing with difficult people, using reference books, how to pull an all-nighter, and much more.