I am a big aviation buff.
In my youth I was majorly into flight sims and the like - Knights of the Sky, Dawn Patrol, TFX, TFX2 Eurofighter, European Air War, IL2, ClOD and so on. I have in my time also made a fair few 3D models (GMax, Blender, Milkshape 3D).
Now I am most taken with building simple replicas on the iPhone. It's a great way to spend my commute.