Contagion's soundtrack (composed by Cliff Martinez) is incredible. One of my favourite of the last 20 years. Cliff Martinez is one of those composers whose work I like so much that will actively seek out the films/shows to which he's attached (see also: Jeff Russo, Bear McCreary, Ramin Djawadi).
That was when I became an instant fan, too. I had seen NARC and Traffic but hadn't really paid attention to the score. I watched the Solaris remake on bluray when it was released and then went to the mall the next day and bought the soundtrack.
Most recently I enjoyed his score for Too Old to Die Young. That was another instant buy.