I never thought I would be ambidextrous. But as I trained with my martial arts teacher pretty intensively over the last 15 years and especially in the last 9 to 10 years using the dha, the Burmese sword, he had us doing double sword work. He said it would give us the ability to utilize the minor hand if the major hand was injured, tired, or if an unexpected target presented itself... It was very difficult at first but has certainly gotten much easier over the years and I found that I can now throw much better with my left hand whether it be a rock, pine cone, a ball or a knife. I have gotten better at shaving left-handed as well as brushing teeth left-handed.
I found that it also opened up my thinking to be able to focus on multiple task, directions, reactions simultaneously. Once patterns of movement were practiced enough that they became ingrained and could be performed unconsciously to keep the dhas from clashing it made it interesting to see how the body would respond when the reactions required didn't necessarily have time for deliberate thought.