My current favorite iPad app is Cogs HD. I had this on my iPhone too but the experience is so much better on the iPad. It's basically a sliding puzzle app (which feels perfect on the touchscreen) but with machine parts. It's really amazing to see the machines come to life on the iPad screen once you complete a puzzle To me, it almost feels like a real novelty gadget puzzler moreso than just another puzzle app
A puzzle app sounds more impressive than a mere novelty gadget to me... that just makes it sound like something that came from a Christmas cracker.