With his old racquet, the drop shots were a lot more frequent... at least that's my feeling. It was so smooth and more often than not impossible for the opponent to reach. But I'd still argue his drop shot is the best one out there.
Paire had some really devilish ones while moving backwards from the baseline. Very hard to counter because you don't know when he'll use it.
Nishikori at his best also had some sweet ones on the forehand side and plays them with good percentages using a stranding strategy. He knows when his opponent is backed up very far and has options to blast or finesse. It hasn't been as great this season as his setup FH has let him down but it's one of my favorite shots of his. You know it is good when Murray doesn't even try to track it down.
I'd also give Ouahab a shout. He hurt GGL and Kohli a lot in Casablanca.