Arsenal have the Chance to Seal the Perfect Signing

A week ago, Arsenal were on top of the Barclays Premier League. Now, the Gunners find themselves in third place after suffering defeat at the hands of rivals Chelsea.
The North Londoners have failed to win in their last three league games and fans are once again worried.
Previously, Arsenal have finished the year on top of the league in 2007-08 and in 2013-14 campaigns and both occasions, they failed to win the title. If the current form continues, they will surely fail once more.

Therefore, Arsenal must reinforce their squad before the winter transfer window shuts down on 1st February and according to reports, they have the chance to seal the perfect signing.
According to Evening Standard, Arsene Wenger has a mammoth transfer kitty of 70 million pounds to seal an exceptional signing this month.
The Gunners have quality and depth in all the departments but not in the strike-force and Wenger must splash the cash to secure a world class goalscorer. However, with only few days left in the transfer window, signing a top star is easier said than done.
In your opinion, who should Arsene Wenger sign?