My favorites right now are:
"Grass-popper" (Grasshopper)
Bi-baby (library)
HIIIIIIIIIIIIIIIIIiiiiiii!!! (usually when you catch him doing something he shouldn't be doing he calls out hi- very loudly) Or he greets everyone in the store like this. It's irresistibly cute.
Mickik (Mickey mouse)
ca-pepa (caterpillar)
Some others that have recently been added to the vocab:
- ice
-cookie (an important one)
- juice
-ink (drink)
- cheese
-pretty much any kind of truck/thing that goes you point to- he can name (firetruck, mail truck, dump truck, cement truck, school bus, train, airplane etc etc.)
- wagon
-mower
-lego
- kitty cat
- moon
- sky
- dirt
- shovel