Tried almost everything I can think of - - - How do I KILL Gophers?

Gas them. ILLEGAL IN CALIFORNIA! Use your vehicle's exhaust to flood the gopher tunnel network with carbon monoxide. Find a way to couple your exhaust pipe to one end of a garden hose, and put the other end of the garden hose in a tunnel. Make sure that you cover any open holes with dirt to keep as much of the exhaust from leaking to the surface as possible. Let your vehicle idle for 15 - 30 minutes to flood the entire tunnel network. Repeat as necessary.
Trap them. Use the gopher traps and place it in the tunnels of an active gopher mound. Dig into the mound and place the trap crossways into the tunnel, then cover the area with a sheet of black plastic or burlap so that no light shines into the hole. It also helps to use latex gloves or rub the trap with fresh rosemary so that it doesn't smell of human scent.
Poison them. Poison baits such as strychnine are very dangerous. Always read all labels and instructions. Be very careful when handling, keep away from children. Wash your hands very thoroughly after handling. This method is not recommended if there is a chance that another animal (such as a pet) could eat the gopher after it is poisoned. If your pet eats a poisoned gopher, it will be poisoned too.
Drown them. Use a garden hose to flood the gopher tunnel with water. Be ready to kill the gopher with a shovel if he quickly pops out of the ground to avoid drowning. This method works about half of the time, but always creates a muddy mess.
Smoke them. Buy gopher flares. Read the instructions, light the flares and fill the tunnel with smoke.
Release a predator. Release a wild gopher snake into an active hole. The snake will clear out a large area -- an acre or more -- before moving on to a new area. Sometimes they stick around for a year or more. Additionally, some domestic cats work well against gophers. Hunting tendencies also depend on the cat's species.
Use a repellent. Repellents are not as effective as other methods. In a glass jar mix 1/2 cup of Castor oil, 1 teaspoon of Tabasco sauce and a few drops of peppermint oil with about a cup of water. Shake well to create an emulsion. Dip cotton balls into the mixture and stick the balls into active gopher holes near plants that you want to protect. Dog "doo" is effective as well. Be sure to wear gloves!
Use gopher baskets. Plant vegetable and other vulnerable plants in gopher baskets. These are baskets made of chicken wire that protect the young roots until they are well established.
Plant gopher spurge. This is a plant that gophers seem to dislike. Plant several in your gopher infested areas.
Feed them Juicyfruit gum. Handle the gum with gloves only so your scent doesn't get on it. Twist the gum, foil and all, and insert it into a fresh mound or a hole you have opened. The gopher will eat it and die in its burrow. Experts scoff at this, perhaps because they get their scent on the gum before they try it. Homeowners swear by it.
Hire a professional. A professional exterminator can use Aluminum Phosphide, which reacts with moisture in the air and soil to produce highly acute toxic phosphine gas. There is no residual poison, and there is no secondary poisoning. If your pet digs up and eats the gopher carcass, there is not a chance that your pet will get poisoned too like many poison baits. This is the most expensive option, but many exterminating companies offer guarantees.
Shoot them. If all else fails a good old crosman 760 pumpmaster usualy does the trick, only about $50. Cheaper than a professional and more fun.