Okay, I'll admit it - I'm already partial to one of the pre-existing robot designs for NXT. I can't wait to get my hands on the NXT system and build it, and I'll tell you why.
Because it looks like it can be fun to chase the cat or dog with... look at those front claws... it might even be fun to put under the bed and let it rush at my wife's ankles when she gets up in the morning (of course, I'll be sleeping on the sofa the next night).
The thing just looks mischievous. I can't wait to program it for various attack scenarios.
And then, of course, there's programming it for sound - barking when chasing the cat, maybe?