We live in an area where we have lots of planes flying overhead. The other day we were outside playing and I pointed out the planes to Evan. He immediately pointed up at the plane and repeated "ahpane". Now whenever we go outside, are driving in the car, or even in the house and he hears an airplane he points and says airplane.
Another word he really likes is bubble. We go outside often to blow bubbles and after trying to keep Evan from constantly eating the bubble mixture when he put the wand in his mouth I decided it would be easier to give him his own empty bubble container and wand. Now he wanders around with it pulling the wand in and out of the container, pretending to blow and saying "bubble".