Acch I've been avoiding this topic for ages because it takes so friggin' long to pick a decent cross-section of my musical tastes, but I'm quite drunk and this'll kill some time. Some favourite artists might be a good way to do it; Against Me!, Mclusky, Aphex Twin, Venetian Snares, Buc 65, Zombieflesheater, the Smiths, Clutch, Discount, Squarepusher, Toots and the Maytals, DJ Vadim, Del Tha Funkee Homosapien, Four Tet, NWA, Boris, Quasimoto, Lamb...all kinds of things. Lots of really frantic breakcore and raggacore when I'm working (Bong-Ra, Shitmat, Knifehandchop; the combination activates my Photoshop devil-hands that can blaze through anything in no time flat), Yann Tiersen or SUNN0))) when I'm reading. Lots of unsorted chiptunes stuff, live scratch DJ sets and rap battles, odds and sods of electronica experiments my friends have sent me to appraise. My life improved immeasurably when I started listening to stuff other than white dudes playing guitars.
Portrait of a Cigarette by Discount is my favourite song ever. I found it on an otherwise unremarkable punk sampler about five years ago, and I must've listened to it a good thousand times since. It's only about a minute and a half long and I've been known to put it on four or five times in a row and not get bored of it.
Dream Theater are a prog metal band, I do not see what's so difficult to pigeonhole.