I will stick up for Adric/Matthew Waterhouse, as he was very young and had not done much acting before becoming Adric. I think the way his character was written didn't help at times either, being a mathematical genius meant that he was rarely going to get along with anyone because it's assumed geniuses are flawed when it comes to talking to others or are seemed to be unapproachable. I liked him as I was a kid growing up and taking in as much Who as possible, he was part of the tardis crew when I first watched it on a regular basis so will always stick up for him and he's a very nice bloke to talk to in the flesh too.
I loved most of the stories with Sarah and the Key To Time with the first Romana, so they would be my top two with Tom.
"You damned courtiers to the Queen, you're nothing but lap dogs to a slip of a girl!"
Hope to meet a nautical cove or two online to chat about Tom, "Who", etc