I liked The Artist Duo the best, they were both really interesting characters who are kinda underrated but definitely powerful. I liked all the duos in the Akatsuki, the only one I wasn't fond of was Itachi and Kisame and that's only because I liked much better as individuals. They're still pretty awesome nonetheless =D
Tobi & Deidara - Most Entertaining ["Tobi is a Good Boy" had very amusing moments with Deidara-senpai] Konan & Nagato - Most Intimidating [I found Nagato under the presence of Pain and Konan quite intimidating] Hidan & Kakuzu - Most Rebellious & Annoying [I'm okay with Kakuzu but Hidan is rebellious and annoying imo] Kisame & Itachi - Most Obedient & Loyal [In One Way or Another] Sasori & Orochimaru - Most Creepy [Both done weird things to their's and others bodies] Sasori & Deidara - Most Effective [Cleanest Jinchuriki Capturing in terms of Power, we've seen to date] Obito & Zetsu -Most Powerful [Zetsu Army + Obito in Prime is Near-Unstoppable]
That's how I view it. Deidara & Sasori are my favorite in terms of villainy together at least. Pain would win this but for some reason, Konan brought him down a few notches. Deidara & Tobi win for amusement.