#4 Didier Drogba
Arsenal's biggest nightmare, Didier Drogba is arguably the best forward bought in the last decade by the Blues.
Since he departed, the club has tried desperately to fill his hole but has been unable to do so.
Drogba was Chelsea's most expensive signing back then, joining the Blues for £24m from Marseille. While many thought it he was not worth spending so much on, Jose Mourinho wanted the striker and was backed by Roman Abramovic.
The Ivorian has won 4 Premier League titles, 4 FA Cups, 3 League Cups, 2 Community Shield and 1 Champions League.
Some of his personal achievements include 2 Premier League Golden Boot, 1 Golden Foot, UEFA Team of The Year, 2 Premier League PFA Team of The Year.
Age is just a number for the 39-year old who is still playing for Montreal Impact and has scored 21 goals in 33 appearances in the last two seasons.
Drogba loved scoring Arsenal and netted 16 goals in as many appearances against them. Just ask any Arsenal fan and they will tell you how the striker would haunt them in their dreams during those times.