dominion probably has the best sountrack in the game, loving the interactions between the game progress (changes in every 25% of nexus health and special when both teams have about 10% left)
new twisted treeline was also nicely made (changes when turrets die and vilemaw is killed)
summoners rift needs a new sountrack, preferably with interactions similar to TT, turrets die - music changes (except for nexus turrets)
its not just because all the other maps have it, but also because the current music is SO BORING!