I usually have my portable CD/MP3 (iRiver IMP-550) player nearby when I play games, so just in case I get tired of the music, I can stick an earbud in one ear, and listen to the sounds effects through the other ear (unless the sound sucks too, which then both ears get stuffed). My earbuds are closed-air earbuds (Sony EX-71LP), so they pretty much block sound out when I use them, so usually only one ear is plugged.
Usually I listen to Jpop albums, anime OSTs, or OP/ED singles.
Usually I listen to Jpop albums, anime OSTs, or OP/ED singles.