Man, your internal jugulars.. They run parallel to your carotid artery. You really don't want to hit your carotid by mistake, you can give yourself a stroke (which could be fatal) if it goes into arteriospasm, which arteries tend to do. It's the artery that supplies a large proportion of your brain. Shooting there could cause a severe haemorrhage as well. If you miss and get an abscess that could be fatal too, an infection in your neck could erode into your carotid or jugular causing a massive haemorrhage, damage nerves and muscles and potentially spread to your head and brain. There are too many important structures in the neck to be going anywhere with a needle, even in a hospital setting they use ultrasound guidance these days.. The external jugular is more superficial and further away from the carotid but it's all far too risky. If you reach this stage you really need to stop shooting.