One of the funniest I heard was regarding SIRI on the new iPhone 4S. Siri, when it understands what you are saying, will do many tasks. So you can say things like "call my mother" and it will dial your mother's number (you will previously have linked the word "mother" to your mother's phone number). It will also respond correctly to questions like " what is the weather like" or "what is the square root of 123".
To make it more personal, you can tell SIRI to use a certain name when addressing you, so you can say "call me Michael", to which it responds "from now on I will call you Michael". So a subsequent weather request might get the answer, "Michael, it is wet outside".
Apparently, someone in a a bit of bother asked SIRI "Call me an ambulance", to which SIRI responded: "From now on I will call you Ann Ambulance".