Saw II
Actual title: Old man ragebaits angry single father for 93 minutes.
Anyway, this is the best in the franchise as I love how we get to learn about John for the first time, how hes such a great antagonist and planned the whole thing.
You also have a pretty good trap set up (even if its weaker than most in the franchise) but my favourite part is with John and Eric.
Of course you also have the classic end of a Saw movie plot twist.