One that could truly provide non biased information, and lack the ability to "create" new information out of thin air to fill in gaps in it's lack of knowledge. It would be nice to see one that is inexpensive and reliable to assist in building apps. I know they are out there but you do pay for what you get!
Another one would be an improved medical diagnostic AI. While some exist there are always problems and can lead you down a rabbit hole if you aren't careful!