Drum roll please. . .
Cycle. As in a motorcycle.
Technically it was a whole phrase all at once; he had never said anything intelligible before, then the other day we were driving home and he saw a motorcycle drive by, and he said, "it's a cycle!"
Now he says it any time he sees a motorcycle. He also says, "it's a car," for cars, and "it's a bus," for anything truck-ish or larger (hey, it's a start). He also likes flipping through the latest issue of Subiesport mag or Subaru Drive Performance mag.
So he's not even two, and all he wants to talk about is cars.