Jigsaw. I wish I could say that it was a great movie that totally redeems the series but, eh, it's Another Saw Movie. Actually, in fairness, it's not bad by the series' standards, and I do like that it's the first movie in the series that has real color in the cinematography, instead of everything being washed out like a 1990s music video. The movie pretty much ignores how the original series ended, with the dirty cop guy becoming the new Jigsaw killer in favor of something else, and it contrives another reason to have Tobin Bell reappear even though he died in something like the 3rd movie (these movies thrive on retcons).
My issue with the series is that I've never bought the psychology they run on. Every single movie involves Jigsaw somehow picking out a bunch of scuzzy but mostly nondescript people with dark secrets and putting them in elaborate death-traps, and every single one of these people reacts by going into instant hysterics and screaming dialogue that includes the word "fuck" a lot, usually while generic industrial music blasts on the soundtrack (now I'm picturing what a Saw movie might look like if the victims were, say, an aging soccer mom, a Hasidic rabbi, a Japanese chef, and tweedy law professor - would they all start screaming "Whatthefuck fuck you bitch asshole motherfucker fuck you!!!" when they wake up? That might actually be fun...). They all go exactly where Jigsaw predicts they'll go, they believe everything he tells them on his little tape recorders even though he's a psycho, and they die in the order they're expected to die in. There's never any accounting for a diversity of responses from the victims and all of them are consistently dim-witted.