Super Mario RPG
Ladies and gentlemen, I present the trophy winner for "Best Elevator Music in a Video Game." At least, the first Booster Tower theme is. I don't think the thrash country or whatever you'd call that second piece is anything anyone would expect to hear in an elevator, or any other public place. But that doesn't make it less awesome.
Booster Tower is probably the most off-the-wall dungeon you'll encounter in any RPG, the one most likely to make you scratch your head, say something along the lines of "WTF?" but still enjoy the hell out of it. Come to think of it, Super Mario RPG in general is that way. It was the easiest RPG ever created, and the storyline is little more than an excuse plot--but the game was fun, dammit. In other words, it's right in Mario flavor.
Booster has nothing to do with Mario at all, of course, and was made up from whole cloth for this game, where you raid his tower, grab the princess (in her last appearance as "Toadstool") and then never think about him again. But as far as zany and random mini-bosses go, Booster is just plain hilarious, and his tower still stands as one of the most fun dungeons in gaming. And this music captures its flavor nicely.