Wood chipper,100 ton stamping press,any number of farm implements,there’s lots of ways to consider.
I’m thinking, the murderer be killed the same way he/she killed their victim. Shot in the face...death by shot to the face.
Slice the victims throat...well.
Sounds gruesome and cruel, but if your state was known for putting to death the guilty by the same means they inflicted on their victims, I believe it would be quite the deterrent.