Saw VI
Damn this might be the best in the franchise. I'll see after rewatching Saw X but this was was really damn good.
The main game with the health insurance guy had some of the best traps and it was actually interesting seeing him have to make moral decisions that oppose the morality he endorces with his health care. Actually a very entertaining way to do political commentary. I really think the carousel trap is the best scene in the series. Also it has Rodrick murdering a guy and that was just badass.
Not only that, the B plot with Hoffman is actually really great too. The scene where they find out he's Jigsaw though the voice scrambler with him then murdering them is pure art. And his whole test thing is also really good too.
Also I was mistaken earlier, the best scene is actually Jigsaw randomly saying "piranha", I haven't laughed so hard at a movie in a long time.
So yeah like 5 of the best scenes of the franchise are in this movie so I think it might just be the best one. Great main game, great B plot and great flashbacks with a solid twist too. Basically the prefect saw movie.