A humpback whale. It is not necessarily anatomically correct.
The .obj file is a bit small, because it was made in Sculptris, in which there is no clear judge of size. That was converted into an stl file in 123d design.
It requires support to print.
Bonus: It floats! (I used 25% infill) Can be used as a bath-toy.
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I don't know if small children could gnaw pieces off.
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For a version with minimal support, see thing 1092504 at http://www.thingiverse.com/thing:1092504