There are a lot of 'nerdy' bands out there that make great backing music for gaming. (Warning - most people won't like my tastes in music).
Australian band The Galvatrons are so hugely influenced by Transformers that their music all sounds very much like the backing to an 80's robot
movie.
Great backing for heaps of different game types:
For things like medieval games and MMOs, there is a band Amon Amarth who sing about Viking mythology and general looting and pillaging. Very apt.
(Melodic Death Metal... maybe?)
( This video even has the metal holy grail: synchonised guitarist hair flipping
)
My recent refound addiction for Titan Quest has left me wanting a new soundtrack to play by, and the new Enter Shikari album is perfect.
(This song even has ATS-style topics like Chem trails and the NWO... double dose of awesome).