4. Zlatan Ibrahimovic
Zlatan Ibrahimovic continues to be one of the most feared strikers in the game. His goalscoring record is excellent, with 75 in 90 appearances for PSG in the last three league seasons. There's no doubt Zlatan would score goals, and would provide United with a towering presence to aim balls at.
Zlatan's ego would suit Manchester United down to the ground. He is a maverick; in the same mould as Eric Cantona with the footballing talent to boot.
The issue here is obviously the Swede's age. He is 33 years-old now, so purchasing him would represent a short-term fix for a season or two. However, it would allow James Wilson to develop and learn from him, whilst also instilling him with the confidence that he will be trusted to lead the line for the reds in the future.
Manchester United need goals, and Zlatan Ibrahimovic is a proven goalscorer. I would give Kane another season or 2 to develop, and go in for Zlatan now. Although he has stated in the past that he wouldn't come and play in England (per the Daily Mail), if United applied some pressure he may well be tempted.