Not a strange cargo per se but very odd crew baggage. One of my instructors at Seattle was ex Pan Am, he told me how on a London trip he saw a Mercedes sports car for sale, I can't remember the model, the price was right so he bought it. When he asked the LHR station manger about getting it shipped to the US the manager told him why not just put a crew tag on it and he would put it in the hold as crew baggage as they were positioning an empty 747 back to JFK.