The Standard Hotel in Downtown LA is pretty cool. Its on the rooftop, the music is a mix of Hip-Hop, House and 80s. The drinks are good, but the view is what makes the place. All of downtown is on display.
Tip: Go Sunday-Thursday and go early (8pm) to avoid a cover and large crowds to get up to the rooftop. Once you're up enjoy the scenery, dont worry it will fill up. If you go Fri-Sat there is a cover of $20 and a chance you wont get upstairs at all.