One of the most unnecessary deaths in the series must surely be Gus' (Tony Nappo) totally-avoidable bullet in the eye number in Saw II. Gus is one of a number of victims trapped inside a house that's slowly filling with a poisonous gas (imagine a slightly less frightful Big Brother house and you're pretty much there).

One of the first commands the group is given is not to use a particular key on the door to the room, so what does Xavier (Franky G) go and do…

How Easy Is It To Achieve? In theory, it's a pretty simple rule. Admittedly, the poison gas makes everything a bit more urgent, and Jigsaw can be a bit tricksy in his wordplay. But don't go and disregard the bleedin' obvious.

If You Really Have To: Make sure you have an idiot like Gus on standby to peer through the peephole and take the bullet for you.