My most successful pairing was for AC Milan... Dzeko as target man and Pato as poacher. I've had similar success in the Championship with Eren Derdiyok as target man and Nilmar as poacher after a year or two.
Benzema and Macheda for Southampton, is still only february and they have scored almost 60 goals between them!! Team has chalked up 140 goals across all competitions
Adebayor and Aguero:
Adebayor is a great Complete forward paired with Aguero as a poacher.
It's not a typical assist goal partnership, it's just they keep out of each others way and cover their weaknesses. So to the feet Aguero is given the goals and if it's in the air Adebayor scores lots.
Scored around 70 goals in a season with this partnership.
My Sporting Lisbon strike partnership is Romelu Lukaku and Yannis Tafer. (Season 6)
In a glourious year which ment playing over 55 games these 2 where almost indespensible with 65 goals between them.
Lukaku - 33 gls - 40 games
Tafer - 32 gls - 45(10) games
Surprisingly Welbeck and Berbatov they really stepped up in my 2012/2013 season when Rooney was out for 9 months. We ended up winning the quadruple and they kept Rooney out of the first team for a lot of the following season