An anatomical model of a human heart, painstakingly assembled from obj files taken from BodyParts3D's database. They claim that I have to say this: "BodyParts3D, Â© The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan"
There are a couple errors in the STL mesh that I couldn't seem to get rid of, but it printed just fine. It seems a little larger than life-size, but I'm not really sure; I've never seen a real human heart. With 1:1 scaling this is nearly as big as a Makerbot Replicator would be able to print.
I used ReplicatorG (skeinforge) with raft and support turned on. "Support Minimum Angle" was set to 85 degrees, so it didn't build very much support at all. I also set the "Support Gap Over Perimeter Extrusion Width" to .015 so the support would detach more easily.