5: Ole Gunnar Solskjaer
Costing a mere £1.5million from Norwegian outfit Molde, Solskjaer arrived at Manchester United with not a single fan having the faintest idea of who he was.
However unlike a large percentage of unknown foreigners who move to the Premier League only to realise they simply can't cut it, Solskjaer went on to play 366 times for the Red Devils, scoring 126 times in the process.
Nicknamed the 'Baby-faced Assassin' because of his youthful appearance and clinical edge, Solskjaer scored the stoppage time winning goal that saw United beat Bayern Munich in the Champions League final of 1999.
That alone is probably worth five times the money Fergie paid for him, but 11 years service as a top quality player puts the icing on the cake.
Solskjaer may have been an underrated super-sub, but he was one of the best pieces of business Fergie ever did.
Wayne Rooney could quite easily have taken this spot, but value for money dictates that it swings in favour of the Norwegian.