I have killed my own food before a number of times. I've killed fish and I have killed chickens. The fish were quick and easy and I felt/feel no guilt for it. I did not enjoy killing the chickens, but then I didn't enjoy killing the fish either. They died at my hands, quickly and with very little pain.

You do realize that these animals are GOING TO DIE regardless, right? Also, most of them would have never existed otherwise. Please tell me which of these two scenarios you think the chicken would prefer:

Scenario 1: Chicken is born and raised on a family farm, is treated well and cared for for years. Then it is killed to be eaten by those that cared for it. They carefully break it's neck, quickly and with little to no pain or pre-anxiety.

Scenario 2: The same chicken is released from the farm. It sees a fox approaching. The fox stalks it for about half an hour, pouncing at it repeatedly until it finally catches its wing in its mouth. It tears the wing off. Now, the bird can't move as easily but is floundering around on the ground. The Fox pounces again and grips it in it's teeth around the birds neck. It presses down firmly with it's teeth, careful not to kill it but silencing it's calls for help. The fox heads back to its den where it places the bird at the mercy of it's pups. They each take turns pouncing on the wounded and bloody bird until finally, it can no longer take it and with the last of it's fight or flight adrenaline, it attempts to burst out the opening of the hole. The mother fox tears open it's neck before it can escape. It bleeds out and becomes their meal.

Which human would like to be killed in a "humane" way?

Many would. Death can be painful and brutal, but it doesn't need to be.

Also, I'm an organ donor. Why? Because after I die, I want my body to be useful.