Ni-Ni (Night Night)
Up (Which can either mean pick me up or put me down. Basically, move me now)
I know there are other words he knows, but he says these consistently.
He can use sign language to say:
When you say "High Five" he gives you a high five.
When you say "Bye bye" he blows kisses. This works whether you are actually saying goodbye or singing the Nsync song.
His favorite book is a Dora the Explorer boardbook, even though he's never seen the show. But he also enjoyed the school bus book when I said "Beep Beep" and poked him in the stomach.
He started this adorable thing where if he wants to sit in your lap he'll walk up to within a foot of you, turn around and slowly reverse backwards into your lap.
He is excellent at ripping off wrapping paper and throwing the paper. And then abandoning the new toy to play with tupperware.
He is also quite skilled at pretending the foam stick give away from the Michigan Basketball game is a sword and stabbing his aunt with the stick. This activity is especially enjoyable if she screams and acts out a prolonged death scene, a la Paul Reubens in Buffy the Vampire Slayer (the movie).