Back in my grade school days, I was referred to as a "human dictionary," due to my (at the time) vast knowledge of words. Now that I think about it, I've learned a lot of said words from games. You know, the games that teachers/parents are always bashing because you supposedly don't learn anything from them, and your time would be much better spent reading books. With that said, I've learned the following from games off the top of my head:
Starcraft
progeny
fervent
incontrovertible
albeit
despondent
latency
dormant
Exile 3: Ruined World (funny thing is, the first thing you see in the game's intro is "exile: verb - to banish or expel)
exile
repertoire
tarry
awkward
smite
dispel
dexterity
agile
ambidextrous
dumbfounded
oaf
Phantasy Star 4
magnanimous
distortion
The Legend of Zelda: Ocarina of Time
malevolent
Diablo
dyslexia
atrophy
Warcraft 3
lethargic
Grandia 2
behest
nostalgic
lament
7th Legion
immolate
equilibrium
Starcraft
progeny
fervent
incontrovertible
albeit
despondent
latency
dormant
Exile 3: Ruined World (funny thing is, the first thing you see in the game's intro is "exile: verb - to banish or expel)
exile
repertoire
tarry
awkward
smite
dispel
dexterity
agile
ambidextrous
dumbfounded
oaf
Phantasy Star 4
magnanimous
distortion
The Legend of Zelda: Ocarina of Time
malevolent
Diablo
dyslexia
atrophy
Warcraft 3
lethargic
Grandia 2
behest
nostalgic
lament
7th Legion
immolate
equilibrium