What has worked for me a few times, and I'm not sure if it's just a peculiarity of my immune system or not: cut as much skin from the surface as possible without risking a bleed, then burn it while pressing down with a red hot piece of metal, paper clip for something small, maybe a little screwdriver if it's larger. Just burn enough that the tissue is damaged below the skin, not enough to reach the root or whatever, probably just around where it would cause a blister on normal skin (which it won't). If it doesn't go away in 10 days do the same thing a few more times. Eventually I get an immune response, the area around the border will turn red, and the thing will just die and not come back. I have had them frozen off at the doctor's before and it's extremely painful, since they'll freeze it way below the skin, unsightly black spots from the blood blister, and usually it ends up growing back, albeit smaller.