Chinese New Year coming up, and 2009 is the Year of the Ox. So I decided to give John Montroll's Ox a try. It's quite hard to get nice details with a 15cm square, so I recommend you fold it from slightly larger paper.
Paper: 15cm square, 65gsm
Model: 7cm length, 3.5cm height, 4cm width (horns)
Someone emailed me asking me about step 28 of this model, so I gave it a try. It's probably a good model for Valentine's Day, with the heart and arrow and all.
Paper: 15cm square of Kraft paper
Finished model: 9cm length, 2.5cm height, 3cm width