To qualify, the ENTIRE song must be in that meter, which excludes a lot of classical music and prog-rock.

• 5/8: Mars, The Bringer of War – Gustav Holst
• 6/8: I Only Have Eyes For You – The Flamingos
• 7/8: What Would I Want? Sky – Animal Collective
• 11/4: Hey Ya – Outkast
• 13/8: All You Need Is Love – The Beatles†
• 21/8: Sail To The Moon – Radiohead
• 3:4 polyrhythm: I'll Believe In Anything – Wolf Parade

†I'm cheating on this one. The chorus switches meter to something slightly less weird.