Beirut's The Flying Cup Club is a strong consideration for the very unique vocal performance and instrumentation.
Bon Iver's For Emma Forever Ago is a strong consideration as an incredible solo journal-esque releases that really let's the emotions flow. It's just an astonishing album.
Kanye West's Graduation took Daft Punk's grandiosity and added his swagger to it. An incredible pop/electro/hip-hop album.
Radiohead's In Rainbows is in contention for one of the band's best albums in their already strong discography. Plus it was released for "free" as one of the first, if not the first, major band/act release in this fashion. It set waves. So in terms of lasting impact, I've gotta give it to In Rainbows.