A non-exhaustive list:
1. Asking "Can you say Daddy?"
2. Saying very sternly "No biting Mama!"
3. Throwing a ball in the air.
4. The cat licking herself.
5. Getting from laying down to standing. (Only when he does so. It's apparently not that funny when others do it).
6. Daddy appearing around corners.
7. Random air molecules above his swing.
8. The dog licking him.
9. Big kids.
10. Jon Stewart.