It really depends...
Dead Can Dance, some Goa Trance tracks when it gets spiritual...
Silent Stream of Goddes Elegy, Dream Teather, Therion and such when it gets dark...
Elend when it gets really dark!!
Rammstein, Paradise Lost, Prodigy, for some combat sequencies (like a pub fight in Orcish underground)
50 cent and others, when it is time to kill some gangstas or posers...
Nine Inch Nails, Frontline Assembly, Kraftwerk, Die Krups etc to get the feeling of the streets, lights, hum and the atmosphere of the night city
Black Sun Empire when it comes to ride a car
ACDC and good old hevy metal for a bike

Morcheeba, US3 and other triphop ilusionists for a good time on the streets

Sepultura, Soulfly, Prodigy, Rob Zombie etc... for major clashes
Hammerfall, Nightwish, Stratovarius etc. for those heroic elves

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old school Cypress Hill...you know...when its time to roll one

And many, many others, what players brought by or the mood asks. Lots of soundtracks, like Matrix, GITS, Heavy Metal 2000, xXx, Platoon, Forest Gump, Full Metal Jacket, Batman...