in Uncharted 4 they felt essential, I liked that A.I.

I remember in Red Alter 3 you could give a lot of commands to your co up general, it worked well, their units where just attacked moved but they helped a lot because you also had a "small" factor of control.

Ellie, Elizabeth, and Quiet had good AI, too. Quiet in particular could be invaluable if you knew how to use her; nothing beats getting caught with your pants down only for her to headshot them in the knick of time.

Not sure what people see in Ashley (is it the ballistics?); she just feels like your typical escort mission to me.

Elizabeth from Bioshock Infinite.  So far the only video game character that really felt like an actual person to me rather than an AI.