QFI with
- duration, melee, bonus power cloak
- increased sticky capacity
- max sabotage
- shocktrooper package + AT-12 raider.
Incredibly fun and incredibly easy to play - with duration/bonus power cloak and max sabotage you're like some invincible ghost, and the Raider makes short work of anything.
I have played duration/bonus power QFI with pistols in the past - probably one of the first kits I ever took to gold, but coming back to it now with shotguns and it's a whole lot of fun. 
Only regret is have to sacrifice melee damage for accuracy and weapon damage for the raider, and secondly have to respec this kit if I want to play with a javelin. But otherwise this is more of a "ghost" than any other infiltrator.