What birds are the best mimics?

I don't know if this question can be answered at all, but lyrebirds are definitely among the candidates. Here is a lyrebird imitating construction workers. Astounding.

https://www.youtube.com/watch?v=C0ZffIh0-NA

Personally I think the question has to be defined - as:
European starling - mimics other birds
Northern mockingbird - mimics other birds and suburban sounds
Steller's Jay - mimics other birds and mammals and suburban sounds
Lyrebird - mimics other birds, mammals, suburban sounds, manmade sounds and musical instruments.

So I am in agreement with wellenbrecher the beautiful shy lyrebird is the one. Scientifically we may be wrong.

Grey parrots are pretty hard to beat. I had a friend that had one and he said listen to this. He opens the door to his garage and the parrot immediately mimicked the garage door going up, the car starting, going into gear, and backing out. Lyrebirds are also amazing.