Donna. She knows how to put the doctor in his place, but she's not so stupid that she won't listen to him when it's important. Plus, the whole 'in love with the doctor' thing is getting old.
I also really love Rose.
I'd have to say Nyssa or Charley.
Both are such sweet characters, with Nyssa's apparent innocence and Charley's love for the doctor.
Also Sarah-Jane Smith was really nice in her episodes and it was so sad to see her go.
In terms of blatant sexiness:
Peri, though she had a slightly annoying accent had her heart in the right place, and I quite enjoyed the earlier episodes she was in. (Then of course, Colin Baker came along and it all became a little boring.)
Amy is just dreamy, the subplot between her and Rory combined with her dreamy accent and semi-revealing clothes, makes her a high contender for best & sexiest companion in my opinion.
Now omgClara... Even though she hasn't been in many episodes so far. Her character is developing really nicely. And I was a fan of Jenna-Louise after she did "Room at the Top."
So I had high expectations and still, she exceeded them.
Ummm....clearly the answer is Amy Pond! She's cute, she's spunky and she loves and feels things very deeply. I love he weird, special relationship she has with The Doctor. And her love with Rory is epic!
(This is going to be long i like to ramble bout Amy >:])
Amy is the best companion she is brave,smart,sweet,and cute. She has had a hard life with becoming an orphan when the crack on the wall killed her parents and then got unintentionally abandoned by the doctor she deserves to have time to travel with him. she is a great middle of all of the companions she is loyal but not obsessed , she loves the doctor(as a friend) but dose'nt follow him around like a puppy she helpful with him , but dosen't spend every min of her live following him. I don't understand how people call her selfish or a brat or pity Rory for having to deal with Amy's insults she is just jokeing around that is how a real relationship works. she dose love him as she takes a 1 out of a billion chance to life her life with him in the angles the Manhattan. She entered the tardis with fillings for him but didn't over step the boundaries like Rose and Martha did. in my opinion she is the most intresting companion with a great back story.
I find this question REALLY hard to answer my first favorite companion was Amy but I'm starting to like Clara and since its taking so long for more episodes to come out I decided to watch from season 1 and I realized ROSE IS SO COOOOOOOOOOOL yeah don't like Donna or Martha though
rose rose rose rose rose . in truth i didnt like donna . but i found it halarious when she told jack to hug her and hes like uuuuuuuuuuh no . (he hugs everybody ) ( lil sex freak :) ) im just bursting with joy over all these ppl who love rose . i miss her so much :(
I really like every one except Martha. Sorry to anyone who likes Martha.
I like Amy because I feel she is very independent and has a life other than the Doctor. I like Clara because she is just.. I just like her. I like Rory because of how sweet and caring he is towards Amy and would do anything to keep her safe. Donna is really funny and tries to do what's right even if the Doctor doesn't agree. I like Rose because she is always willing to do what is right even if it puts herself in danger, like in doomsday. I like River and Jack for the same reason: they are awsome!
I do not like Martha because I feel she is very reliant on the Doctor. Also she can be quite insensitive.