Avery has a few. He does a knock on the door sound, without actually banging on anything. Sometimes it's so spot on that the dogs get barking and running to the door. He also has learned my older son's laugh, and chimes in with it whenever he hears something funny, and always before any of us start laughing. We have to check if our son is nearby or it's the bird. Baxter usually chimes in with her full on woman's belly laugh.
Avery and Tucker both have learned the neighbor's dog bark, and it sounds exactly like them barking from outside, through closed windows. We haven't heard it in a while, but Tucker must have lived near someone with a foreign car. Imagine a Volkswagen bug horn beeping. He's fooled us several times that made us look out the window to see if someone was in the driveway beeping.