Visible crew/equipment: In the crushing room at the end of the film, Strahm is trying to open the box where Hoffman is. As it's descending into the ground, on the side of the box you can see the feet of a crew member with white sneakers moving around. It is not Strahm's feet: he's wearing black boots. No slow-mo is required.
Trivia: (Spoiler) Strahm is killed by the walls of the final room crushing him. However, in the original script, rather than the walls crushing, the room was supposed to fill with water, thus mirroring that trap that nearly killed Strahm in the beginning of the movie. Due to practicality reasons, this idea was dropped, though it does explain the air-tubes coming of the glass box. (Which would have been for Strahm to breath.)
Trivia: Patrick Melton and Marcus Dunstan, the writers of both "Saw IV" and "Saw V", have a cameo in the flashback of Hoffman being kidnapped and meeting Jigsaw for the first time. When Hoffman is about to get on the elevator right before getting kidnapped, Dunstan is the second man to exit the elevator (he is in black and has a beard), right after the snobbish woman. Melton is the tall man who exits the elevator last before Hoffman enters.TedStixon
Trivia: The coffin trap at the end of the movie, in which the walls move in, is based on a drawing done by director David Hackl's young son. (DVD extras)
Jigsaw: Hello, Agent Strahm. If you're hearing this, then you've finally found what you've been looking for. But is the discovery of my body enough? Or will your insatiable hunger to uncover the truth push you deeper into the abyss? Heed my warning: do not proceed. For this room can either be you sanctuary, or it can be your grave. The choice is yours.
Agent Strahm: Fuck you.
Jigsaw: Hello Seth, I want to play a game. Right now, you are feeling helpless. This is the same helplessness you bestowed onto others. But now, it's unto you. Some would call this karma, I call it justice. Now you served five years of what should have been a life sentence, for murder. A technicality gave you freedom, but it inhibited you from understanding the impact of taking a life. Today, I offer you true freedom. In thirty seconds, the pendulum will drop far enough to touch your body. Within sixty seconds, it will cut you in half. To avoid the pendulum, all you have to do is destroy the things that have killed... Your hands. You must insert your hands and push the buttons to start the devices before you. Your bones will be crushed to dust. Will you destroy the things that have taken life in order to save one, Seth? Make your choice.
Question: It's explained that Hoffman wanted to be the hero and that he expected that no one would make it out alive in the building after Rigg's game. How in the world could he have expected or even decided this? He had no control over others who won their game in the building, so therefore how on earth could he predict that Strahm would kill Jeff in the previous film? And was the water cube intended to kill Strahm as he was warned not to proceed?