I liked Ace, mostly because she could stand up for herself instead of screaming and needing to be rescued every five minutes. She was also a great relief after Bonnie Langford
I also liked Romana (the Lalla Ward incarnation) and K9.
Whistler"I wonder wonder why the wonder falls. I wonder why the wonder falls on me. I wonder wonder why the wonder falls, with everything I touch and hear and see."
I'm sorry but Ace sucked big time!! I just wanted to smack her one every time she called the Doctor 'Professor'!! Grrrr
Anyway, there are so many to chose from, it's a bit of a toughie. But, Jo, from Pertwee's incarnation was good on the eye As was Nyssa from Baker's/Davison's
But, Turlough was one of the more interesting ones. You were never always sure where his loyalties lay.