With a quick search and face value looking, you can die standing up. It happens when the body immediately cools after a physical activity and causes the muscles to stiffen up.
Well, there is an open space at the bottom middle of the ribcage, the knife and be angle up as you stab to get to the hear; if not the heart, then cutting the arteries and what not to cause major injury and death.
A few things I learned:
A person kind die by a broken heart, literally. It's called Broken Heart Syndrome; it causes the effects of a heart attack, but is not a heart attack. So it is easily treatable; but because of the short term heart muscle, one can still die though rarely.
Your tongue has a lot of connective tissues and blood vessels running through it, so if you were to bite/cut it off, you could die of blood loss, choke to death by your own blood, or etc,.
The body eats itself prior upon death because the cells and what not are not getting the essentials they need and their toxicity/acidity increases, eating away at the body.
An addition to the above; a lot of gases builds up in the body, causing it to bloat. It is best not tamper with the body at this point because the gases are condensed and could blow out violently; it's reasons why you are told to stay away from dead, beached whales.
Temperature can hide how long a person has been dead for. Cold temperatures causes the body to stiffen up and warm temperatures can make it seem like it is fresh.
You can kill some one by just injecting air into their blood stream; this is because it causes air embolism and a large enough embolism, depending in which part of the body it is in, can be fatal. If you inject ~2-3 mL of air into the artery, it can go to the brain to cause cerebral embolism and it triggers a stroke. Inject 0.5-1 mL of air into the pulmonary vein can cause a cardiac arrest.